A gradient structure 3D printed metal component and its preparation process

Abstract

The present invention discloses a gradient structure 3D printed metal component and its preparation process, belonging to the field of 3D printing forming preparation. The preparation process of the present invention includes: 1) 3D printing material preparation, 2) 3D model construction and parameter setting, 3) 3D printing forming, 4) mechanical treatment, 5) surface treatment, and finally obtaining a 3D printed metal component with a dense surface without pores and excellent mechanical properties. The present invention solves the problems of material surface densification and pores by introducing laser peening technology into the preparation process of 3D printed metal components, and solves the problem of crack propagation by introducing a pulsed electric field during the laser peening process, thereby preparing high-quality gradient structure 3D printed metal components.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing and forming, and in particular to a gradient structure 3D printed metal component and a preparation process thereof. Background Art

[0002] 3D printing technology is an emerging technology. Compared with traditional material synthesis and manufacturing processes, it can produce complex or customized parts in a shorter production cycle. It has been widely used in the manufacturing of personalized biological implants, large and complex aerospace engine blades and discs, and thermonuclear reactor vacuum vessels. 3D printing technology is a powder-based additive manufacturing process that uses a laser beam to selectively melt thin layers of metal powder in a layered manner and control it by cutting a 3D design model. This method is not only attractive in rapid prototyping, but also in the manufacture of complex components. 3D technology can better solve the problems of traditional processing technology that are difficult to prepare complex products and difficult to form. However, defects such as pores, poor fusion, and cracks will appear in the 3D printing process, and even the rapid cooling of the molten pool will cause residual tensile stress on the surface of the part. This will greatly affect the service performance of 3D printed products.

[0003] Laser shot peening (LSP) is a promising surface modification technology. LSP uses high-frequency, short laser pulses to pass through the confinement layer and then impact the workpiece surface. LSP technology has broad application prospects in the field of micro-surface engineering. LSP can improve the fatigue resistance, wear resistance and corrosion resistance of metals, and has been significantly applied in the field of materials. For example, Chinese patent CN112809022A discloses a new method for additive preparation of metal parts, which uses a combination of metal 3D printing and laser shot peening to prepare metal parts. By introducing laser shot peening during the printing process, laser shock strengthening is performed when each layer of the forming layer is not fully solidified, or laser shock strengthening is performed on the metal cladding while printing. The patent has the following technical defects: 1) The use of layer-by-layer printing and laser shot peening is time-consuming and labor-intensive, the operation process is complicated, the production efficiency is low, and it is not conducive to industrial promotion and application; 2) Introducing laser shot peening in each layer can increase the density of each layer and improve the material properties, but it will also introduce deformation stress and affect the dimensional accuracy of the final molded part. Summary of the invention

[0004] The purpose of the present invention is to provide a gradient structure 3D printed metal component and a preparation process thereof. The present invention solves the problems of surface density and porosity of 3D printed materials by introducing laser shot peening technology into the preparation process of 3D printed metal components after printing and molding, and solves the problem of crack propagation by introducing a pulse electric field during the laser shot peening process, thereby preparing high-quality gradient structure 3D printed metal components.

[0005] The technical solution adopted by the present invention is:

[0006] A process for preparing a gradient structure 3D printed metal component comprises the following steps:

[0007] (1) Preparation of 3D printing materials: metal powder with a particle size of less than 100 μm was selected and placed in an oven to dry the water;

[0008] (2) 3D model construction and parameter setting: construct a 3D printing model, set the corresponding 3D printing parameters, and import it into the 3D printing equipment;

[0009] (3) 3D printing: Use a laser cladding 3D printer to print and obtain metal parts;

[0010] (4) Mechanized processing: removing the support parts on the surface of metal parts by wire cutting;

[0011] (5) Surface treatment: Laser shot peening is performed on both sides of the metal parts at the same time, and a pulse current is introduced into the metal parts during the shot peening process;

[0012] (6) Produce gradient structure 3D printed metal parts.

[0013] Preferably, in step (1), the oven temperature is 50-150° C., and the drying time is 30-60 min.

[0014] Preferably, the purity of the metal powder in step (1) is above 99%.

[0015] Preferably, in step (2), the parameters of 3D printing are: laser power 500-700 W, scanning speed 400-650 mm / min, powder feeding rate 0.2-20 r / min, layer thickness 0.2-0.5 mm.

[0016] Preferably, in step (3), the laser is a continuous laser, the number of channels of the laser cladding head is ≥ 3, and argon gas is used for powder delivery throughout the process.

[0017] Preferably, in step (5), the power of laser shot peening is >200 W, the laser pulse time is 25 s to 30 s, the spot diameter is 0.1 to 5 mm, and the shot peening time is 1 min to 30 min.

[0018] Preferably, in step (5), pulse current transmitters are installed on the longitudinal section and cross section of the 3D printed metal parts, respectively, and the pulse current of the pulse current transmitter is controlled to be 0.1 to 10 A and the pulse time is 25 s to 30 s.

[0019] A gradient structure 3D printed metal component is made by any one of the above-mentioned gradient structure 3D printed metal component preparation processes.

[0020] Furthermore, the thickness of the gradient structure 3D printed metal parts after removing the base is above 0.5 mm.

[0021] Beneficial effects of the present invention:

[0022] (1) In view of the technical defects of pores and looseness in existing 3D printed metal parts, the present invention eliminates the pores on the product surface and improves the density of the product surface by laser shot peening on both surfaces of the metal parts after printing. At the same time, it can also produce gradient structure in the metal parts, thereby improving the mechanical properties of the metal parts as a whole.

[0023] (2) In response to the technical defect of cracks in existing 3D printed metal parts, the present invention adopts the "thermal effect" and "skin effect" of electric pulses to allow the current to gather and generate heat at the crack tip, causing the crack to melt and promote the "healing" of the crack, thereby solving the crack problem of metal parts.

[0024] (3) The present invention introduces an electric field during the shot peening process to allow the laser and the electric field to interact with each other. On the one hand, the electric field thermal effect can suppress the stress concentration of the laser energy field on the product surface, making the thickness of the laser shot peening layer thicker, thereby producing a more obvious gradient ultrafine structure and reducing defects such as pores and cracks inside the product. That is, the electric field promotes the effect of the laser energy field. On the other hand, the laser energy field gives the material a gradient structure, that is, the number of grain boundaries at different positions is different, thereby having different obstacles to the current, so that the current can play a good effect on the "healing" of cracks in different areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a metallographic image of the 3D printed metal component in Example 1 in the thickness direction after laser shot peening.

[0026] Figure 2 This is a metallographic image of the 3D printed metal parts in the thickness direction after laser shot peening in Example 2. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with specific examples to facilitate understanding of the present invention, but the present invention is not limited thereto.

[0028] Implementation Case 1

[0029] A gradient structure 3D printed metal component, the preparation process of which is as follows:

[0030] Step 1, 3D printing material preparation: Purchase 5 kg of 316L stainless steel 3D printing metal powder with a purity of 99% and a particle size of 50 μm to 150 μm, then screen the metal powder, select about 4 kg of metal powder with a particle size below 100 μm, and bake it in an oven at 50°C for 30 minutes.

[0031] Step 2, 3D model construction and parameter setting: Use Solidworks software to build a 3D printing model with a length, width and height of 50mm×30mm×20mm, set the laser power to 500W, the scanning speed to 400mm / min, the powder feeding rate to 0.2r / min, the layer thickness to 0.2mm, generate G code, and import it into the 3D printing equipment.

[0032] Step 3, 3D printing: Use a continuous laser with a 3-channel laser cladding head to print in layers in sequence, and use argon gas to deliver powder throughout the process to produce plasma to prevent oxidation of the molten pool.

[0033] Step 4, post-printing mechanized processing: remove the surface support by wire cutting to obtain a 3D printed metal part with a thickness of 19 mm.

[0034] Step 5, laser shot peening coupled electric pulse surface treatment: Use shot peening equipment with a laser power of 200W to shot peen the 3D printed metal parts obtained in step 4, the laser pulse time is 25s, the spot diameter is 0.1mm, and the shot peening time is 30min. During the shot peening process, pulse current emitters are installed on the longitudinal section and cross section of the 3D printed parts respectively, where the pulse current of the cross section emitter is 10A, the pulse time is 25s, and 3 pulse current emitters are installed from top to bottom on the longitudinal section, the currents are 10A, 5A and 10A respectively, and the pulse time is 25s. The use of current in both the longitudinal and transverse directions can make the electric field fully play a role, so that the current can have a better effect on the "healing" of cracks in different areas.

[0035] Step 6, obtaining gradient structure 3D printed metal parts.

[0036] A small sample of 1 cm × 1 cm × 3 cm in length, width and height was cut from the gradient structure 3D printed metal parts obtained in step 6, and its gradient structure was observed. A gradient structure of about 2.4 cm thick was seen, extending from the surface to the center. The grain size of the microstructure was reduced, and there were no micro defects such as cracks, pores, and looseness. Figure 1 shown. Figure 1 Half the thickness of the product is shown, and the arrows point from the edge of the product to the center of the product.

[0037] The above-mentioned small sample was subjected to mechanical property tests at different strain rates, and the tensile properties are shown in Table 1. As can be seen from Table 1, the yield strength, tensile strength and elongation of the gradient structure 3D printed metal parts of the present invention are relatively excellent.

[0038] Table 1

[0039] Strain rate 1 / s Yield strength MPa Tensile strength MPa Elongation % <![CDATA[10 -3 ]]> 643 812 20 <![CDATA[10 -4 ]]> 612 800 24.2

[0040] Implementation Case 2

[0041] A gradient structure 3D printed metal component, the preparation process of which is as follows:

[0042] Step 1, 3D printing material preparation: Purchase 1 kg of 304 stainless steel 3D printing metal powder with a purity of 99% and a particle size in the range of 50 μm to 150 μm, then screen the metal powder, select about 0.7 kg of metal powder with a particle size below 100 μm, and bake it in an oven at 150°C for 60 minutes.

[0043] Step 2, 3D model construction and parameter setting: Use Solidworks software to build a 3D printing model with a length, width and height of 50mm×30mm×5mm, set the laser power to 700W, the scanning speed to 650mm / min, the powder feeding rate to 0.5r / min, the layer thickness to 0.5mm, generate G code, and import it into the 3D printing equipment.

[0044] Step 3, 3D printing: Use a continuous laser with a 4-channel laser cladding head to print in layers in sequence, and use argon gas to deliver powder throughout the process to generate plasma to prevent oxidation of the molten pool.

[0045] Step 4, post-printing mechanized processing: remove the surface support by wire cutting to obtain a 3D printed metal part with a thickness of 4.8 mm.

[0046] Step 5, laser shot peening coupled electric pulse surface treatment: Use shot peening equipment with a laser power of 700W to shot peen the 3D printed metal parts obtained in step 4, the laser pulse time is 30s, the spot diameter is 0.1mm, and the shot peening time is 1min. During the shot peening process, pulse current emitters are installed on the longitudinal section and cross section of the 3D printed metal parts respectively, where the pulse current of the cross-sectional emitter is 0.1A, the pulse time is 30s, and 1 pulse current emitter is installed on the longitudinal section, the current is 1A, and the pulse time is 30s.

[0047] Step 6, obtaining gradient structure 3D printed metal parts.

[0048] A small sample of 1 cm × 1 cm × 0.5 cm in length, width and height was cut from the 3D printed metal parts obtained in step 6, and its gradient structure was observed. A gradient structure of about 0.2 cm thick was seen, extending from the surface to the center. The grain size of the microstructure was reduced, and there were no micro defects such as cracks, pores, and looseness. Figure 2 shown. Figure 2 Half the thickness of the product is shown, and the arrows point from the edge of the product to the center of the product.

[0049] The mechanical properties of the above small specimens were tested at different strain rates, and the tensile properties are shown in Table 2.

[0050] Table 2

[0051] Strain rate 1 / s Yield strength MPa Tensile strength MPa Elongation % <![CDATA[10 -3 ]]> 700 925 20％ <![CDATA[10 -4 ]]> 702 893 26％

[0052] Implementation Case 3

[0053] A gradient structure 3D printed metal component, the preparation process of which is as follows:

[0054] Step 1, 3D printing material preparation: Purchase 10 kg of 316L stainless steel 3D printing metal powder with a purity of 99.9% and a particle size in the range of 50 μm to 150 μm, then screen the metal powder, select about 8.6 kg of metal powder with a particle size below 100 μm, and bake it in an oven at 150°C for 60 minutes.

[0055] Step 2, 3D model construction and parameter setting: Use Solidworks software to build a 3D printing model with a length, width and height of 50mm×30mm×1mm, set the laser power to 700W, the scanning speed to 650mm / min, the powder feeding rate to 0.4r / min, the layer thickness to 0.2mm, generate G code, and import it into the 3D printing equipment.

[0056] Step 3, 3D printing: Use a continuous laser with a 4-channel laser cladding head to print in layers in sequence, and use argon gas to deliver powder throughout the process to generate plasma to prevent oxidation of the molten pool.

[0057] Step 4, post-printing mechanized processing: remove the surface support by wire cutting to obtain a 3D printed metal part with a thickness of 0.5 mm.

[0058] Step 5, laser shot peening coupled electric pulse surface treatment: Use shot peening equipment with a laser power of 200W to shot peen the 3D printed metal parts obtained in step 4, the laser pulse time is 30s, the spot diameter is 5mm, and the shot peening time is 10min. During the shot peening process, pulse current emitters are installed on the longitudinal section and cross section of the 3D printed parts respectively, where the pulse current of the cross-sectional emitter is 0.1A, the pulse time is 30s, and 3 pulse current emitters are installed on the longitudinal section, with currents of 10A, 1A and 10A respectively, and the pulse time is 30s.

[0059] Step 6, obtaining gradient structure 3D printed metal parts.

[0060] The mechanical properties of the gradient structure 3D printed metal parts prepared in step 6 were tested at different strain rates, and the tensile properties are shown in Table 3.

[0061] Table 3

[0062] Strain rate 1 / s Yield strength MPa Tensile strength MPa Elongation % <![CDATA[10 -3 ]]> 721 896 21.2％ <![CDATA[10 -4 ]]> 711 882 24.3％

[0063] Implementation Case 4

[0064] A gradient structure 3D printed metal component, the preparation process of which is as follows:

[0065] Step 1, 3D printing material preparation: Purchase 6 kg of 316L stainless steel 3D printing metal powder with a purity of 99.5% and a particle size in the range of 50 μm to 150 μm, then screen the metal powder, select about 5.3 kg of metal powder with a particle size below 100 μm, and bake it in an oven at 100°C for 50 minutes.

[0066] Step 2, 3D model construction and parameter setting: Use Solidworks software to build a 3D printing model with a length, width and height of 60mm×20mm×10mm, set the laser power to 500W, the scanning speed to 550mm / min, the powder feeding rate to 0.5r / min, the layer thickness to 0.2mm, generate G code, and import it into the 3D printing equipment.

[0067] Step 3, 3D printing: Use a continuous laser with a 6-channel laser cladding head to print in layers in sequence, with a powder feeding rate of 10r / min. Argon is used for powder feeding throughout the process to generate plasma to prevent oxidation of the molten pool.

[0068] Step 4, post-printing mechanized processing: remove the surface support by wire cutting to obtain a 3D printed metal part with a thickness of 5.2 mm.

[0069] Step 5, laser shot peening coupled electric pulse surface treatment: Use shot peening equipment with a laser power of 700W to shot peen the 3D printed metal parts obtained in step 4, the laser pulse time is 30s, the spot diameter is 2mm, and the shot peening time is 20min. During the shot peening process, pulse current emitters are installed on the longitudinal section and cross section of the 3D printed parts respectively, where the pulse current of the cross-sectional emitter is 5A, the pulse time is 30s, and 3 pulse current emitters are installed on the longitudinal section, with currents of 10A, 5A and 10A respectively, and the pulse time is 30s.

[0070] The mechanical properties of the gradient structure 3D printed metal parts prepared in step 6 were tested at different strain rates, and the tensile properties are shown in Table 4.

[0071] Table 4

[0072]

[0073]

[0074] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications are also within the scope of protection of the present invention.

Claims

1. A preparation process for gradient structure 3D printed metal components, characterized in that, it includes the following steps: (1) 3D printing material preparation: Screen metal powders with a particle size below 100 μm and place them in an oven to dry the moisture; (2) 3D model construction and parameter setting: Construct a 3D printing model, set the corresponding 3D printing parameters, and import them into the 3D printing device; (3) 3D printing and forming: Use a laser cladding type 3D printer for printing to obtain metal components; (4) Mechanical processing: Remove the support on the surface of the metal components by wire cutting; (5) Surface treatment: Simultaneously perform laser shot peening on both sides of the metal components, and introduce pulsed current into the metal components during the shot peening process; (6) Obtain gradient structure 3D printed metal components; In step (5), the power of laser shot peening > 200W, the laser pulse time is 25s - 30s, the spot diameter is 0.1 - 5mm, and the shot peening time is 1min - 30min; In step (5), install pulsed current emitters on the longitudinal section and cross section of the 3D printed metal components respectively, and control the pulsed current of the pulsed current emitter to be 0.1 - 10A, and the pulse time to be 25s - 30s.

2. The preparation process for gradient structure 3D printed metal components according to claim 1, characterized in that, in step (1), the oven temperature is 50 - 150°C, and the drying time is 30 - 60min.

3. The preparation process for gradient structure 3D printed metal components according to claim 1, characterized in that, the purity of the metal powder in step (1) is above 99%.

4. The preparation process for gradient structure 3D printed metal components according to claim 1, characterized in that, in step (2), the 3D printing parameters are: laser power 500 - 700W, scanning speed 400 - 650mm / min, powder feeding rate 0.2 - 20r / min, layer thickness 0.2 - 0.5mm.

5. The preparation process for gradient structure 3D printed metal components according to claim 1, characterized in that, in step (3), the laser adopts continuous laser, the channel of the laser cladding head ≥ 3, and argon powder feeding is adopted throughout the process.

6. A gradient structure 3D printed metal component, characterized in that, it is made by the preparation process for gradient structure 3D printed metal components according to any one of claims 1 - 5.

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