An internal defect closing post-processing method for 3D printing alloy plate

Abstract

The application belongs to the technical field of post-processing of metal additive manufacturing, and particularly discloses an internal defect closing post-processing method for 3D printing alloy plate. The method first performs step-by-step polishing on the upper surface, then positions the sample in the groove body of a steel mold, uniformly applies vacuum silicon grease on the surface of the sample, and sets a high-explosive-speed plate-shaped plastic explosive; then, the whole device is placed in a static explosion site, an electronic detonator is installed at one end of the explosive and detonation is implemented, the internal cracks are subjected to plastic closing by using the shock loading of detonation impact; finally, the sample after impact treatment is placed in a vacuum muffle furnace for heat treatment, so as to promote the further diffusion, combination and healing of the crack interface, and obtain a 3D printing alloy plate with healed cracks. The above method can effectively repair the internal cracks, and has the advantages of large treatment depth, controllable deformation, short process cycle and low cost.

Description

Technical Field

[0001] This invention belongs to the field of metal additive manufacturing post-processing technology, specifically relating to a method for closing internal defects in 3D printed alloy sheets. Background Technology

[0002] Metal 3D printing technology, with its advantages of high-precision forming, lightweight manufacturing, and high material utilization, is widely used in the fabrication of alloy components in key fields such as aerospace, high-end equipment, and energy. However, this manufacturing process is generally accompanied by inherent process characteristics such as poor dynamic stability of the molten pool, uneven powder melting, and extremely rapid cooling and solidification. These characteristics make the formed alloy components highly susceptible to various defects such as unfused porosity and interlayer microcracks. These defects not only disrupt the continuity and homogeneity of the material structure but also become stress concentration points or crack initiation sources when the components are subjected to tensile, alternating fatigue, and impact loads. This significantly reduces the matrix strength, plasticity, and fatigue life of the 3D printed alloy, greatly limiting the large-scale application of 3D printed alloys in high-end load-bearing components and long-life service components.

[0003] Currently, the industry has developed various post-processing technologies for internal defects in 3D printed alloys. Mainstream processes include hot isostatic pressing (HIP), conventional heat treatment, and surface strengthening treatment. However, significant technical limitations remain. HIP, relying on creep and diffusion under high temperature and pressure to close pores, is currently the most widely used method for repairing defects in 3D printed alloys. However, its high temperature easily leads to significant grain growth, resulting in decreased material strength and toughness. Furthermore, this process is costly and time-consuming, and its furnace size limits its suitability for efficient batch processing of large components. It also has limited effectiveness in repairing large or surface-connected unfused cracks. Conventional heat treatment processes such as simple annealing and solution treatment can only release residual internal stress in 3D printed alloys, failing to close large internal pores or deep microcracks. Surface strengthening processes such as laser impact and mechanical shot peening have only a limited effective modification depth on the component's surface, optimizing only the surface microstructure and stress state, but failing to reach the subsurface and deep core defects, thus hindering the repair of deep defects.

[0004] In summary, existing 3D printed alloy defect closure post-processing technologies generally suffer from multiple technical bottlenecks, such as easy grain coarsening, poor defect healing quality, insufficient effective repair depth, and easy damage to component precision. They are difficult to meet the multiple requirements of efficient defect closure, matrix structure stability, and improved mechanical properties. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention provides a post-processing method for closing internal defects in 3D printed alloy sheets. This post-processing method can effectively repair internal cracks and has advantages such as large processing depth, controllable deformation, short process cycle, and low cost, making it suitable for post-processing repair.

[0006] To achieve the above objectives, the present invention adopts the following specific technical solution: In a first aspect, the present invention provides a method for post-processing the closure of internal defects in 3D printed alloy sheets, the method comprising the following steps: Step 1: Grind and polish the upper surface of the 3D printed alloy sheet to remove the surface oxide layer and burrs, making the surface smooth and clean. Step 2: Place and confine the 3D printed alloy sheet within the groove of the steel mold; Step 3: Apply a layer of vacuum silicone grease evenly to the upper surface of the 3D printed alloy sheet, so that the vacuum silicone grease covers the upper surface of the 3D printed alloy sheet to form a continuous thin layer of vacuum silicone grease. Then, lay a layer of rigid plastic film on top of the thin layer of vacuum silicone grease. The vacuum silicone grease and the rigid plastic film together form a protective layer. Step 4: Place the high-explosive-velocity plate-shaped plastic explosive flat on the top surface of the protective layer, and ensure that the high-explosive-velocity plate-shaped plastic explosive is tightly adhered to the protective layer. Step 5: Transfer the assembled steel mold, 3D printed alloy sheet, vacuum silicone grease, hard plastic film and high-explosive-velocity plate-shaped plastic explosive as a whole to the static detonation site and place it on a flat and stable ground to ensure stability during the detonation process. Step 6: Insert an electronic detonator into one end of the high-explosive-velocity plate-shaped plastic explosive; Step 7: Detonate the electronic detonator to generate a detonation impact of the high-explosion-velocity plate-shaped plastic explosive, thereby applying an impact load to the 3D printed alloy sheet to obtain a 3D printed alloy sheet with closed cracks. Step 8: The 3D printed alloy sheet after impact loading is placed in a vacuum muffle furnace for heat treatment to heal the internal cracks of the 3D printed alloy sheet and obtain a crack-healed 3D printed alloy sheet.

[0007] Furthermore, in step one, the 3D printed alloy sheet is polished step by step using SiC sandpaper with a mesh size of 300-2000.

[0008] Furthermore, in step two, the steel mold is made of 45# steel or stainless steel; Furthermore, there is a clearance fit between the 3D printed alloy sheet and the groove of the steel mold.

[0009] Furthermore, in step three, the thickness of the vacuum silicone grease coating is 0.05mm-0.1mm; the rigid plastic film is made of PVC and has a thickness of 0.2mm-0.5mm.

[0010] Furthermore, high-explosive-velocity plate-shaped plastic explosives can be castable powder explosives, plastic plate-shaped explosives, or rubber plate-shaped explosives.

[0011] Furthermore, the high-explosive-velocity plate-shaped plastic explosive is a C4 explosive with a detonation velocity of 6000-8000 m / s, a thickness of 5 mm, and a density of 1.3-1.5 g / cm³. 3 .

[0012] Furthermore, the impact loading of 3D printed alloy sheets can be repeated 1-3 times using high-explosive plate-shaped plastic explosives.

[0013] Furthermore, in step eight, the heat treatment process parameters are: heat treatment temperature 800℃-1100℃, heating rate 10℃ / min, holding time 1h, and water cooling after the holding time is completed.

[0014] Secondly, the present invention also provides a 3D printed alloy sheet obtained by post-processing any of the internal defect closure post-processing methods provided by the above-mentioned technical solutions.

[0015] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: 1. The internal defect closure post-treatment method of the present invention uses high-explosive plate-shaped plastic explosive to detonate and impact 3D printed alloy plates. Relying on the plastic compaction effect generated by the high-energy impact, the internal pores are compressed, squeezed, and tightly closed, which can effectively close internal pores and microcracks within a depth range of 0-5mm on the surface of the 3D printed alloy plate. At the same time, combined with the heat treatment process in a vacuum muffle furnace, it can promote the release of residual stress after impact, the recovery of the structure in the local plastic deformation zone, and the diffusion welding and interface bonding of the crack tip, thereby achieving further crack healing, improving the continuity, density, and structural integrity of the crack closure area, and breaking through the depth limitation of traditional shot peening, laser impact and other processes that can only achieve surface modification, thus significantly improving the defect closure quality.

[0016] 2. In the internal defect closure post-processing method of the present invention, a steel mold is used as a special constraint tooling to circumferentially limit the 3D printed alloy sheet, which can effectively limit the macroscopic deformation of the 3D printed alloy sheet during the processing, ensure the dimensional accuracy of the 3D printed alloy sheet, and further improve the mechanical properties of the matrix.

[0017] 3. Compared with the traditional hot isostatic pressing repair process, the internal defect closure post-treatment method of the present invention has lower equipment investment cost, simpler processing flow, shorter process cycle, and stronger adaptability and practicality. It can meet the defect repair and performance enhancement needs of mass 3D printed alloy plates, and also takes into account the multiple needs of efficient defect closure, matrix structure stability, and mechanical property improvement. Attached Figure Description

[0018] Figure 1 This is a flowchart of the method for post-closure treatment of internal defects in 3D printed alloy sheets according to the present invention; Figure 2 This is a schematic diagram of the overall structure used in the explosive impact treatment of the internal defect closure post-treatment method of the present invention.

[0019] Figure 3 This is a scanning electron microscope (SEM) backscattered image of a 3D printed alloy sheet.

[0020] Figure 4 Metallographic optical microscope (OM) image of the final product prepared in Example 1.

[0021] Figure 5 Metallographic optical microscope (OM) image of the final product prepared in Example 2.

[0022] Figure 6 Metallographic optical microscope (OM) image of the final product prepared in Example 3.

[0023] Figure label: 1-Electronic detonator, 2-Explosive, 3-Protective layer, 4-3D printed alloy sheet, 5-Steel mold. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This embodiment provides a 3D printed alloy sheet 4, which is obtained by post-processing using an internal defect closure post-processing method, wherein, as... Figure 1 As shown, the post-closure treatment method for internal defects includes the following steps: Step 1: Use sandpaper of different grits to polish the upper surface of the 3D printed alloy sheet 4 to remove the oxide layer, burrs and obvious processing marks on the surface of the 3D printed alloy sheet 4, so that the surface to be treated is flat and clean. When using sandpaper to polish the surface, SiC sandpaper of 300-2000 grit can be used to polish the 3D printed alloy sheet 4 step by step.

[0026] Step 2: Place the 3D printed alloy sheet 4 into the groove of the steel mold 5; the steel mold 5 is a prefabricated part used to circumferentially limit the 3D printed alloy sheet 4. The steel mold 5 has a groove with an opening on the top surface, and the groove is shaped to fit the 3D printed alloy sheet 4; the material of the steel mold 5 is 45# steel or stainless steel; there is a clearance fit between the 3D printed alloy sheet 4 and the groove of the steel mold 5.

[0027] Step 3: A layer of vacuum silicone grease is uniformly coated onto the upper surface of the 3D-printed alloy sheet 4, forming a continuous thin layer. This vacuum silicone grease improves the adhesion between the high-velocity plate-shaped plastic explosive and the surface of the 3D-printed alloy sheet 4. A rigid plastic film is then laid on top of the vacuum silicone grease layer, forming an interface protective layer together. The thickness of the vacuum silicone grease coating is 0.05mm-0.1mm. The rigid plastic film is made of PVC and has a thickness of 0.2mm-0.5mm.

[0028] Step four: Place the high-detonation-velocity plate-shaped plastic explosive 2 flat on the top surface of the protective layer, ensuring a tight seal between the high-detonation-velocity plate-shaped plastic explosive 2 and the protective layer. The high-detonation-velocity plate-shaped plastic explosive 2 is a pre-assembled explosive, which can be castable powder explosive, plastic plate explosive, or rubber plate explosive, preferably C4 explosive; the high-detonation-velocity plate-shaped plastic explosive 2 has a detonation velocity of 6000-8000 m / s, a thickness of 5 mm, and a density of 1.3-1.5 g / cm³. 3 .

[0029] Step 5: Transfer the assembled steel mold 5, 3D printed alloy sheet 4, vacuum silicone grease, hard plastic film, and high-explosive-velocity plate-shaped plastic explosive 2 as a whole to the static detonation site and place them on a flat and stable ground to ensure stability during the detonation process.

[0030] Step six: Insert the electronic detonator 1 into one end of the high-velocity plate-shaped plastic explosive 2, and complete the connection and assembly of the electronic detonator 1 and the high-velocity plate-shaped plastic explosive 2 before detonation.

[0031] Step seven involves detonating the electronic detonator 1 to generate a detonation impact from the high-velocity plate-shaped plastic explosive 2, thereby applying an impact load to the 3D-printed alloy sheet 4 and obtaining a 3D-printed alloy sheet 4 with closed cracks. In practice, depending on the thickness and other specific conditions of the 3D-printed alloy sheet 4, the high-velocity plate-shaped plastic explosive 2 can be used to repeatedly apply the impact load 1-3 times to the 3D-printed alloy sheet 4.

[0032] Step eight involves placing the 3D-printed alloy sheet 4, after impact loading, into a vacuum muffle furnace for heat treatment. By controlling the temperature and holding time of the heat treatment, the internal cracks in the 3D-printed alloy sheet 4 are healed, resulting in a crack-healed 3D-printed alloy sheet 4. The heat treatment process parameters in the vacuum muffle furnace are: heat treatment temperature 800℃-1100℃, heating rate 10℃ / min, holding time 1 hour, and water cooling after the holding time.

[0033] In the following specific embodiments and comparative examples: Scanning electron microscopy (SEM) testing: A Hitachi S-4800 field emission scanning electron microscope was used, with an accelerating voltage of 5kV. Optical microscopy (OM) metallographic characterization: The macroscopic morphology, porosity, and crack defects of the 3D-printed alloy sheet 4 were observed using a Nikon ECLIPSE MA200 inverted metallographic microscope, and microstructure images were acquired. Sample preparation and microstructure inspection were performed according to GB / T 13298-2015 "Metallic Microstructure Inspection Method". Hardness testing: A micro Vickers hardness tester (FM-700) was used, with a pressure of 2.94N and a holding time of 15s. The dimensions of the steel mold 5 are 200mm × 150mm × 20mm; the thickness of the 3D-printed alloy sheet 4 is 10mm, and the sheet width is 130mm × 6mm; the thickness of the C4 explosive is 5mm. The overall structure used in the explosive impact treatment is as follows: Figure 2 As shown, the steel mold 5 is placed on the pre-laid sand pile, the 3D printed alloy plate 4 is placed in the groove of the steel mold 5, a layer of vacuum silicone grease is evenly applied to the surface of the 3D printed alloy plate 4 to be detonated, a PVC plastic film is placed on the silicone grease to form a protective layer 3, the pressed C4 explosive is laid on the surface of the protective layer 3, the electronic detonator 1 is inserted, the electronic detonator 1 and the detonator are connected to initiate the detonation.

[0034] Example 1 The above-mentioned internal defect closure treatment method was used to process the 3D printed alloy sheet sample 4. The sample was subjected to an explosive impact once using C4 explosive. The heat treatment temperature was 900℃ when heat treatment was carried out in a vacuum muffle furnace.

[0035] Figure 3The image shows a SEM image of a high-entropy alloy sample prepared by 3D printing. The image reveals that the sample has many cracks and pores inside. Figure 4 The OM results of the sample treated with this method show that the internal cracks of the sample disappeared after explosive hardening combined heat treatment.

[0036] Example 2 The above-mentioned internal defect closure post-treatment method was used to process 4 samples of 3D printed alloy sheet. The samples were subjected to an explosive impact once using C4 explosive. The heat treatment temperature was 1000℃ when heat treatment was carried out in a vacuum muffle furnace.

[0037] Figure 3 This is an optical microscope image of a high-entropy alloy sample prepared using 3D printing technology. The image shows that there are many cracks and pores inside the sample. Figure 5 The OM results of the sample treated with this method show that the internal cracks of the sample disappeared after explosive hardening combined heat treatment.

[0038] Example 3 The above-mentioned internal defect closure post-treatment method was used to process 4 samples of 3D printed alloy sheet. The samples were subjected to an explosive impact once using C4 explosive. The heat treatment temperature was 1100℃ when heat treatment was carried out in a vacuum muffle furnace.

[0039] Figure 3 This is an image of a high-entropy alloy optical microscope prepared using 3D printing technology. The image shows that there are many cracks and holes inside the sample. Figure 6 The OM results of the sample treated with this method show that the internal cracks of the sample disappeared after explosive hardening combined heat treatment.

[0040] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the invention. Therefore, if these modifications and variations fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

[0041] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for post-processing of internal defect closure in 3D printed alloy sheets, characterized in that, Includes the following steps: Step 1: Grind and polish the upper surface of the 3D printed alloy sheet to remove the surface oxide layer and burrs, making the surface smooth and clean. Step 2: Place and confine the 3D printed alloy sheet within the groove of the steel mold; Step 3: Apply a layer of vacuum silicone grease evenly to the upper surface of the 3D printed alloy sheet, so that the vacuum silicone grease covers the upper surface of the 3D printed alloy sheet to form a continuous thin layer of vacuum silicone grease. Then, lay a layer of rigid plastic film on top of the thin layer of vacuum silicone grease. The vacuum silicone grease and the rigid plastic film together form a protective layer. Step 4: Place the high-explosive-velocity plate-shaped plastic explosive flat on the top surface of the protective layer, and ensure that the high-explosive-velocity plate-shaped plastic explosive is tightly adhered to the protective layer. Step 5: Transfer the assembled steel mold, 3D printed alloy sheet, vacuum silicone grease, hard plastic film and high-explosive-velocity plate-shaped plastic explosive as a whole to the static detonation site and place it on a flat and stable ground to ensure stability during the detonation process. Step 6: Insert an electronic detonator into one end of the high-explosive-velocity plate-shaped plastic explosive; Step 7: Detonate the electronic detonator to generate a detonation impact of the high-explosion-velocity plate-shaped plastic explosive, thereby applying impact loading to the 3D printed alloy sheet to obtain a 3D printed alloy sheet with closed cracks. Step 8: The 3D printed alloy sheet after impact loading is placed in a vacuum muffle furnace for heat treatment to heal the internal cracks of the 3D printed alloy sheet and obtain a crack-healed 3D printed alloy sheet.

2. The method for post-treatment of internal defects in 3D printed alloy sheets as described in claim 1, characterized in that, In step one, the 3D printed alloy sheet is polished step by step using SiC sandpaper with a mesh size of 300-2000.

3. The method for post-closure treatment of internal defects in 3D printed alloy sheets as described in claim 1, characterized in that, In step two, the steel mold is made of 45# steel or stainless steel.

4. The method for post-closure of internal defects in 3D printed alloy sheets as described in claim 1, characterized in that, The 3D printed alloy sheet is fitted with a clearance between the groove of the steel mold.

5. The method for post-closure of internal defects in 3D printed alloy sheets as described in claim 1, characterized in that, In step three, the thickness of the vacuum silicone grease coating is 0.05mm-0.1mm; the rigid plastic film is made of PVC and has a thickness of 0.2mm-0.5mm.

6. The method for post-closure treatment of internal defects in 3D printed alloy sheets as described in claim 1, characterized in that, High-explosive-velocity plate-shaped plastic explosives can be castable powder explosives, plastic plate-shaped explosives, or rubber plate-shaped explosives.

7. The method for post-closure of internal defects in 3D printed alloy sheets as described in claim 6, characterized in that, The high-velocity plate-shaped plastic explosive is a C4 explosive with a detonation velocity of 6000-8000 m / s, a thickness of 5 mm, and a density of 1.3-1.5 g / cm³. 3 .

8. The method for post-closure of internal defects in 3D printed alloy sheets as described in claim 1, characterized in that, The impact loading of 3D printed alloy sheets can be repeated 1-3 times using high-explosive-velocity plate-shaped plastic explosives.

9. The method for post-treatment of internal defect closure in 3D printed alloy sheets as described in any one of claims 1-8, characterized in that, In step eight, the heat treatment process parameters are: heat treatment temperature 800℃-1100℃, heating rate 10℃ / min, holding time 1h, and water cooling after holding.

10. A 3D printed alloy sheet obtained by post-processing using the internal defect closure post-processing method as described in any one of claims 1-9.

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