A method of additive manufacturing of a porous material

Abstract

The application relates to the field of additive manufacturing material processing technology, and particularly discloses a method for manufacturing porous material by additive manufacturing, which comprises the following steps: manufacturing a solid part model of the required porous material, slicing the model by layers by using slicing software, and 3D printing metal powder by using an additive manufacturing technology SLM method, so that the lap joint rate of the molten pool is controlled to be above 80%, thereby making the internal elements of each molten pool fully evaporate to form pores, and obtaining the porous material. The application can greatly simplify the preparation process, does not need auxiliary materials to help the porous material forming, can avoid the introduction of impurities, and is favorable for the homogenization of microstructure and material performance. In addition, since the pores of the porous material are caused by element evaporation, the pores are spherical, the inside is empty, and there is no residual powder in the pores.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of additive manufacturing material processing, and particularly relates to a method for additive manufacturing of porous material. BACKGROUND

[0002] Porous material is a material with a spatial network structure of internal interconnected or closed pores. Compared with continuous medium material, it can obtain lower relative density, higher specific surface area and higher permeability while keeping the specific strength approximately unchanged, and can also expand the application of the material, such as being used as a lightweight thermal insulation material.

[0003] Metal additive manufacturing porous material has the advantages of low cost and low surface roughness. At present, the methods for additive manufacturing of porous material include binder jetting and light solidification forming, but these methods need resin and other materials to assist in forming, and the resin needs to be removed in the subsequent process to obtain the porous material, which is complicated and easy to introduce impurities into the porous material. SUMMARY

[0004] In view of the deficiencies in the prior art, the application provides a method for additive manufacturing of porous material, which sets the energy density to be high enough (more than 150 J / mm 3 , and ensures that the overlap rate of the molten pool is controlled to be more than 80% during 3D printing, so that the elements inside each molten pool are fully evaporated to form pores, thereby printing the porous material. This method can greatly simplify the preparation process, does not need auxiliary materials to help the porous material to form, and can avoid the introduction of impurities, which is beneficial to the uniformization of microstructure and material performance.

[0005] To achieve the above-mentioned purposes, the technical scheme adopted by the application is as follows:

[0006] The application provides a method for additive manufacturing of porous material, which comprises the following steps:

[0007] Step 1: using a three-dimensional modeling software to design a solid porous part model which does not need to be evacuated inside, and setting the additive manufacturing process parameters, wherein the energy density needs to be more than 150 J / mm 3 , and performing layer-by-layer slicing processing on the part model according to the designed layer thickness;

[0008] Step 2: designing a printing strategy corresponding to the morphology of the porous material to be obtained in the software;

[0009] Step 3: screening out metal powder corresponding to the layer thickness, and drying for standby use;

[0010] Step 4: using an external heat source to 3D print the powder on the substrate plane by an additive manufacturing method, so that the overlap rate of the molten pool is controlled to be more than 80%, so that each molten pool is fully evaporated to form pores, and after printing is completed, the internal residual metal powder is removed to obtain the required porous material.

[0011] As a further illustration of the present application, the porous material comprises at least one of intermetallic compound, titanium alloy, aluminum alloy. Preferably, the porous material comprises at least one of AlSi10Mg, Ti-6Al-4V, Ti-48Al-2Nb-2Cr, TC4.

[0012] As a further illustration of the present application, the additive manufacturing process parameters include scanning speed, power range, scanning strategy, layer thickness setting; wherein the scanning speed is 100-7000 mm / s; the power range is 50-500W; the scanning strategy can be selected from single-direction scanning strategy, single-direction rotation alternating scanning strategy, back-and-forth scanning strategy, back-and-forth rotation alternating strategy, chessboard (island) scanning strategy, wherein the rotation angle is 0-360°; the layer thickness is 20-70 μm.

[0013] As a further illustration of the present application, the particle size distribution of the metal powder used for the porous material conforms to the normal distribution, and the average particle size should correspond to the size of the software slice layer thickness of the material, and the two should be similar or consistent; preferably, the material layer thickness is a, wherein a is greater than zero, and the particle size D50 of the metal powder is a, wherein a is greater than zero; preferably, the software slice layer thickness is between 20-70 μm, and the particle size of the metal powder is between 15-75 μm.

[0014] As a further illustration of the present application, the metal powder is sieved to obtain a powder with a particle size range of a-b, wherein a and b are both greater than zero, and the layer thickness c is equal to (a+b) / 2.

[0015] As a further illustration of the present application, in step 3, the drying process comprises: after the raw material metal powder is vacuumized in the drying box, heating and holding, and then cooling to room temperature; wherein the heating temperature t=100-200 ℃, the holding time T=4-6 h, and the cooling method is furnace cooling.

[0016] As a further illustration of the present application, in step 4, the external heat source is at least one of laser, plasma, and electron beam.

[0017] As a further illustration of the present application, in step 4, the method for removing the internal residual metal powder includes at least one of cutting, mechanical pounding, ultrasonic vibration, grinding, and erasing.

[0018] As a further illustration of the present application, in step 4, the substrate material used in the 3D printing process is the same material as the porous material or a material with similar composition.

[0019] When the substrate material used is not the same material as the porous material, the cut-off part includes the part where the microstructure of the material at the junction of the substrate and the resulting porous material is different from other areas. Preferably, the part to be cut off should be about 2-5 times the layer thickness higher than the substrate plane.

[0020] Compared with the prior art, the present application has the following beneficial technical effects:

[0021] In the present application, the lap joint rate of the molten pool is controlled to be more than 80%, even more than 90% when 3D printing, so that the internal elements of each molten pool are fully evaporated to form pores, thereby printing a porous material. This method can greatly simplify the preparation process, without the need for auxiliary materials to help the porous material to form, while avoiding the introduction of impurities, which is beneficial to the homogenization of the microstructure and the material properties. In addition, since the pores of the porous material are caused by the evaporation of elements, the pores are spherical and empty inside, and there is no residual powder in the pores. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The flow chart of the preparation method of the porous material is shown.

[0023] Figure 2 The scanning strategy diagram for designing the porosity of the porous material is shown.

[0024] Figure 3 The scanning electron microscope image of the spoon-shaped pore generated by the evaporation of elements caused by high energy input of the porous material is shown.

[0025] Figure 4 The schematic diagram of the spoon-shaped pore generated by the evaporation of elements caused by high energy input of the porous material is shown. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0027] The materials, tools and equipment used in the embodiments of the present application are commercially available materials, tools and equipment unless otherwise specified.

[0028] In this embodiment, the metal pre-alloyed rod is prepared into a metal powder raw material by a vacuum electrode induction melting gas atomization method.

[0029] The embodiment adopts a planetary ball mill to mix different metal powders into a uniform powder raw material.

[0030] The embodiment of the application uses a BLT-S210 selective laser melting device to perform additive manufacturing.

[0031] As shown in Figure 1 The preparation method of the hierarchical porous material provided by the application specifically comprises the following steps:

[0032] (a) using a three-dimensional modeling software to design a solid porous part model which does not need to be evacuated inside, then designing a printing strategy corresponding to a porous material topography which needs to be obtained, which can be designed as a one-way scanning strategy, a one-way rotating alternating scanning strategy, a back-and-forth scanning strategy, a back-and-forth rotating alternating strategy, a chessboard (island) scanning strategy, as shown in Figure 2 Then, layer thickness, power, layer thickness, line scanning speed and other parameters of the equipment are set, and then the model is processed layer by layer and the corresponding engineering file is generated;

[0033] (b) screening the metal powder raw material, and obtaining spherical powder with a maximum particle size of about 2-3 times the corresponding layer thickness height, then placing it in a drying oven to avoid the interference of air moisture and other impurities on the printing process;

[0034] (c) selecting a metal substrate with a clean and smooth surface which is the same as or similar to the composition of the printed material, placing it on the additive manufacturing printing work platform, placing the dried metal powder in the powder supply bin of the equipment, and installing a scraper;

[0035] (d) manually operating the scraper to uniformly spread the first layer of powder on the work platform, then sealing the equipment, and passing high-purity argon gas to control the oxygen content below 0.05 %, and preheating the substrate to reduce the warping phenomenon caused by material thermal stress. The method uses the principle of high-energy input to produce element evaporation as the principle of generating porous materials, as shown in Figure 4 Generally, the overlap rate of the melting track gap is controlled to be above 80 %, and after the preheating is completed, the printing work is started, and the powder spreading and printing are performed layer by layer until the printing is completed.

[0036] (e) after the printing is completed, when the substrate temperature is reduced to room temperature, the substrate is taken out, the metal powder around the porous material is removed, and the substrate is cut off to obtain a complete porous material, and the pores in the porous material are controlled by the scanning pitch parameter.

[0037] Embodiment

[0038] A preparation method of a TC4 porous metal material, mainly applied in the field of aerospace, wherein the method mainly comprises the following steps:

[0039] Step 1: Model the porous material using three-dimensional modeling software, the porosity of the part is designed to be 30%, and the size of the part is 10 mm*10 mm*10 mm;

[0040] Step 2: Use software to set the 3D printing process parameters of the material, such as power, scanning speed, scanning interval. Select power 250W, scanning speed 150mm / s, scanning interval 100um, select 60um layer thickness, under this parameter design, more than 200 J / mm 3 Energy density input, much larger than the required 40-50 J / mm 3 Energy input to form a dense block, more conducive to obtaining more pores in the printed block. Then slice the modeling file, generate an engineering file, and import it into the device;

[0041] Step 3: Select TC4 powder with particle size distribution of 15-53 μm, and sieve the powder with 200 mesh sieve, select powder with particle size below 75 μm, and put it into the drying oven, set the drying oven heating temperature to 200℃, after 6h of heat preservation, cool to room temperature with the furnace;

[0042] Step 4: Place the TC4 powder dried and cooled to room temperature in the powder supply bin of the S210 device, select a clean and smooth TC4 titanium alloy substrate, fix it on the laser working platform with bolts, and install the scraper, then manually operate the scraper to lay the first layer of powder needed for printing on the working platform;

[0043] Step 5: Close the device and pass argon gas, control the oxygen content in the working chamber to be below 0.0.5%, turn on the external laser heat source, and selectively melt the first layer of powder to obtain the first layer of porous material structure;

[0044] Step 6: Operate the device to start repeating the powder laying and selective laser melting operations until the complete porous material part is obtained. After the substrate cools to room temperature, clean the powder around the substrate and the porous material, and cut off the substrate to obtain a complete TC4 porous material.

[0045] The porous material structure prepared in this example is shown in Figure 3 As can be seen from the figure, the part has holes of 5-50 μm, which makes the part have a larger specific surface area and can better play a heat insulation role.

[0046] It has to be noted that, as used herein, such terms as "including", "contains" or any other variations thereof are intended to cover a non-exclusive inclusion, such that processes, methods, articles, or apparatuses that comprise a list of elements are not required to comprise only those elements recited, but can also include other elements not expressly listed or inherent to such processes, methods, articles, or apparatuses.

[0047] While embodiments of the application have been shown and described, it is to be understood that the application is not limited to the details of the embodiments described, since numerous modifications and changes can be made to the embodiments without departing from the spirit and scope of the application as defined by the appended claims and their equivalents.

Claims

1. A method for additive manufacturing of porous materials, characterized in that, The method includes the following steps: Step 1: Design a solid, porous part model that does not require internal hollowing using 3D modeling software, and set the additive manufacturing process parameters, including scanning speed, power range, scanning strategy, and layer thickness settings; wherein, the scanning speed is 100–7000 mm / s; the power range is 50–500 W; the scanning strategy is selected from unidirectional scanning strategy, unidirectional rotational alternating scanning strategy, reciprocating scanning strategy, reciprocating rotational alternating strategy, and checkerboard scanning strategy, wherein the rotation angle is 0–360°; the layer thickness is 20–70 μm, and the energy density must be greater than 200 J / mm². 3 The part model is then sliced ​​layer by layer according to the designed layer thickness. Step 2: Design the printing strategy in the software to obtain the morphology of the porous material; Step 3: Sieve out the metal powder of the corresponding layer thickness and dry it for later use; the particle size distribution of the metal powder used in the porous material conforms to a normal distribution, and its average particle size should correspond to the thickness of the software slice layer of the material. The thickness of the software slice layer is between 20 and 70 μm, and the particle size of the metal powder is between 15 and 75 μm. Step 4: Using additive manufacturing, the powder is 3D printed on the substrate plane using an external heat source, and the overlap rate of the molten pool is controlled at more than 80%, so that the elements inside each molten pool are fully evaporated to form pores. After printing, the residual metal powder inside is removed to obtain the desired porous material.

2. The method for additive manufacturing of porous materials as described in claim 1, characterized in that, The porous material includes at least one of intermetallic compounds, titanium alloys, and aluminum alloys.

3. The method for additive manufacturing of porous materials as described in claim 1, characterized in that, The metal powder is sieved to obtain powder with a particle size range of a~b, where both a and b are greater than zero. Then the layer thickness c is equal to (a+b) / 2.

4. The method for additive manufacturing of porous materials as described in claim 1, characterized in that, In step 3, the drying process includes: evacuating the raw material metal powder in a drying oven, heating and holding it at that temperature, and then cooling it to room temperature; wherein the heating temperature t = 100~200 ℃, the holding time T = 4~6 h, and the cooling method is furnace cooling.

5. The method for additive manufacturing of porous materials as described in claim 1, characterized in that, In step 4, the external heat source is at least one of laser, plasma, and electron beam.

6. The method for additive manufacturing of porous materials as described in claim 1, characterized in that, In step 4, the methods for removing residual metal powder inside include at least one of cutting, mechanical hammering, ultrasonic vibration, grinding, and wiping.

7. The method for additive manufacturing of porous materials as described in claim 1, characterized in that, In step 4, the substrate material and the porous material used in the 3D printing process are the same material or have similar composition.

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