An ultrasonic roll assisted additive manufacturing method and apparatus

Abstract

The application discloses an ultrasonic rolling assisted laser additive manufacturing method and device, and belongs to the technical field of additive manufacturing. The ultrasonic rolling system is fixed on the laser deposition device through a support, and a forming base plate is fixed in a cooling water tank, so that synchronous ultrasonic rolling and temperature regulation and control are realized on a deposited layer in an additive process. By applying ultrasonic vibration in a molten pool solidification stage, grains are refined, and internal defects are reduced. The rolling module adopts a roller type structure design, ensures effective ultrasonic transmission, utilizes the integrated ultrasonic vibration roller to apply high-frequency vibration pressure behind the molten pool, generates plastic deformation on the material in a high-temperature plastic state, reduces residual stress, improves surface roughness, densifies and optimizes the microstructure. Through water cooling temperature control, the influence of thermal accumulation of the deposited layer on the ultrasonic rolling layer is reduced, the interlayer organization consistency is improved, and the overall organization uniformity regulation and performance improvement of the laser additive manufacturing component are realized.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology and relates to an ultrasonic rolling-assisted laser additive manufacturing method and apparatus. Background Technology

[0002] Laser additive manufacturing (LAM) technology uses a high-energy laser beam to melt metal powder or wire layer by layer, achieving near-net-shape forming. It can directly manufacture metal parts with complex geometries, showing great potential in aerospace, biomedicine, and mold making. However, while LAM can form complex components, the continuous deposition process is hampered by severe temperature gradients and rapid cooling rates that induce high residual tensile stress, leading to deformation and cracking. Simultaneously, heat accumulation results in significant differences in interlayer microstructure, affecting the uniformity of the overall properties of the formed part. Furthermore, rapid solidification of the molten pool tends to form coarse columnar and dendritic structures, leading to anisotropic material properties. Insufficient molten pool flow and other factors can easily generate internal defects such as porosity and lack of fusion, as well as high surface roughness. The combined effect of these problems often results in lower fatigue performance and fracture toughness of LAM-formed parts compared to forgings of the same composition. Therefore, achieving uniformity in the overall microstructure and properties of LAM-formed parts is a pressing issue that needs to be addressed.

[0003] Currently, forced interlayer cooling can control the layer temperature to some extent, but it cannot solve the problems of intralayer microstructure and residual stress. Surface ultrasonic rolling applies pressure to the formed part after deposition, which can improve surface quality, but cold rolling requires large pressure and only acts on the surface of the formed part, making it impossible to regulate the overall microstructure and properties of the formed part.

[0004] Chinese invention patent CN 118287688 A discloses a method for preparing titanium alloy materials using ultrasonic-assisted additive manufacturing. This patent applies ultrasonic vibration to a titanium alloy substrate during arc additive manufacturing, utilizing cavitation and convection to promote the breakup of columnar crystals and the formation of equiaxed crystals. While this method can promote microstructure uniformity, the ultrasound can only act on the molten pool, limiting its effectiveness. Furthermore, since the ultrasonic device is located at the bottom of the substrate, the ultrasonic effect gradually weakens with increasing deposition height, resulting in a diminishing impact.

[0005] Chinese invention patent CN119870513B discloses a cooling device and method for additive manufacturing equipment. This patent employs a plate-type cooling structure with upper and lower cooling plates, increasing the contact area between the upper plates and effectively avoiding the risk of mechanical collisions during contact and movement with the formed part, thus ensuring cooling efficiency. Furthermore, placing the first cooling block outside the forming chamber isolates it from the high-temperature and dusty environment, improving safety. While this method can reduce heat accumulation, it cannot achieve overall cooling of the formed part, thus limiting its ability to control the overall uniformity of the formed part.

[0006] Chinese invention patent CN 116021037 A discloses a ball-bearing ultrasonic micro-forging assisted additive manufacturing device. This patent employs a double-layer ball structure, with a mounting base attached to the ultrasonic micro-forging head. An arc-shaped groove is formed on the side of the mounting base away from the ultrasonic amplitude transformer, and multiple small balls are evenly arranged on the inner wall of the groove, surrounding a larger ball. This structure results in minimal ultrasonic energy attenuation, achieving micro-area ultrasonic rolling and improving the uniformity of the formed part's microstructure. However, due to the ball structure, the contact with the formed part is point-to-point, making it difficult to achieve high-efficiency high-temperature plastic deformation. Summary of the Invention

[0007] To overcome the problems existing in the prior art, this invention proposes an ultrasonic rolling-assisted laser additive manufacturing method and apparatus, which achieves overall microstructure uniformity control and performance improvement of laser additive manufactured parts. This invention integrates ultrasonic vibration, rolling plastic deformation, and water-cooled temperature control during the additive manufacturing process to achieve overall microstructure uniformity control and performance improvement of laser additive manufactured components, solving the problems of coarse grains, porosity defects, high residual stress, and poor interlayer microstructure consistency inherent in single additive manufacturing processes.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: An ultrasonic rolling-assisted laser additive manufacturing apparatus includes a laser deposition forming system, an ultrasonic rolling system, a water cooling system, and a control system 15.

[0009] The laser deposition forming system includes a laser deposition device 2, a deposition height monitoring sensor 7, a deposition layer 8, and a forming substrate 10. The deposition height monitoring sensor 7 is fixed to the side of the cooling water tank 6 and connected to the control system 15. The deposition height monitoring sensor 7 can monitor the deposition height of the deposition layer 8 in real time and transmit the signal to the control system 15. The laser deposition device 2 is connected to the control system 15. The forming substrate 10 is fixed to the bottom surface of the cooling water tank 6. The powder or filament at the end of the laser deposition device 2 gathers on the forming substrate 10, is melted by laser, and forms the deposition layer 8 along a predetermined deposition trajectory. During the process, the height of the coolant in the cooling water tank 6 is lower than the height of the deposition layer 8 on the forming substrate 10.

[0010] The ultrasonic rolling system includes a pneumatic module, an ultrasonic module, and a rolling module, specifically: The pneumatic module includes an air pump 16, a pressure regulating valve 17, a solenoid valve 18, an air pipe 19, and a cylinder 20. The air pump 16 generates high-pressure gas, which is transmitted through the air pipe 19. The air pipe 19 is equipped with a pressure regulating valve 17 and a solenoid valve 18. The high-pressure gas passes through the pressure regulating valve 17 and the solenoid valve 18 in sequence and acts on the cylinder 20. The cylinder 20 is fixed on a bracket 1. The bracket 1 is connected to the laser deposition device 2. The pressure of the high-pressure gas output from the cylinder 20 is controlled by the pressure regulating valve 17. The solenoid valve 18 is connected to the control system 15 and is used to control the extension and retraction of the cylinder 20 to realize the movement of the ultrasonic module and the rolling module.

[0011] The ultrasonic module includes an ultrasonic transducer 3, an ultrasonic amplitude transformer 4, and an ultrasonic generator 14. The top of the ultrasonic transducer 3 is connected to the cylinder 20, and the bottom of the ultrasonic amplitude transformer 4 is installed. The ultrasonic transducer 3 is connected to the control system through the ultrasonic generator 14 to realize the control of ultrasonic power, frequency, on and off. The ultrasonic waves are transmitted to the deposition layer 8 through the ultrasonic amplitude transformer 4 and the rolling module in sequence, which accelerates the flow speed of the molten pool and realizes the intervention and control of the molten pool.

[0012] The rolling module includes a rolling bracket 5, a roller 21, and a roller 22. The rolling bracket 5 is fixed to the end of the ultrasonic amplitude transformer 4 by a threaded connection. The roller 22 is connected to the rolling bracket 5 by a thread to reduce ultrasonic attenuation during the process and ensure effective ultrasonic transmission. The roller 21 is cylindrical, and its circumferential surface rolls in contact with the deposition layer 8 to increase the rolling contact area. The roller 22 coaxially passes through the inside of the roller 21. The roller 21 and the roller 22 are assembled with a clearance fit, so that the roller 21 rotates with the roller 22, reducing frictional resistance and ensuring the stability and continuity of the rolling process. The retraction of the cylinder 20 drives the rolling module away from the deposition layer 8. The extension of the cylinder 20 drives the rolling module to press the deposition layer 8, so that the roller 21 and the deposition layer 8 are in close contact, generating rolling force. The ultrasonic rolling system moves synchronously with the laser deposition forming system to roll the high-temperature area behind the molten pool of the deposition layer 8.

[0013] The water cooling system includes a cooling water tank 6, water pipes 9, a temperature sensor 11, a liquid level monitoring sensor 12, and a water chiller 13. The temperature sensor 11 and the liquid level monitoring sensor 12 are fixed to the side of the cooling water tank 6. The temperature sensor 11 monitors the temperature of the coolant in the cooling water tank 6 in real time, and the liquid level monitoring sensor 12 monitors the liquid level of the coolant in the cooling water tank 6 in real time and transmits the signals to the control system 15. The water chiller 13 is connected to the control system 15. The control system 15 controls the water chiller 13 based on the signals fed back to the control system 15 from the temperature sensor 11 and the liquid level monitoring sensor 12, and adjusts the temperature and level of the coolant in the cooling water tank 6 in real time through the water chiller 13.

[0014] Furthermore, the temperature sensor 11 is a resistance temperature sensor or a thermocouple temperature sensor, and the liquid level monitoring sensor 12 is a laser displacement sensor.

[0015] Furthermore, the rolling support 5 is fixed to the end of the ultrasonic amplitude transformer 4 by a threaded connection, and the roller 22 is connected to the rolling support 5 by a thread to reduce the attenuation of ultrasound during operation and ensure effective transmission of ultrasound. The rolling support 5 and the roller 22 are made of mold steel or high-temperature alloy, and the roller 21 is made of ceramic or high-temperature alloy to prevent the roller 21 from wearing and contaminating the deposit layer 8 during the rolling process, and at the same time to prevent the roller 21 from sticking to the deposit layer 8 and damaging the deposit layer 8.

[0016] Furthermore, the coolant in the water-cooling system is water and a mixture of water with ethylene glycol, propylene glycol and water-cooling additives.

[0017] Furthermore, the laser deposition forming system is a powder-feeding laser deposition forming system, a wire-feeding laser deposition forming system, or a wire-powder combined laser deposition forming system.

[0018] An ultrasonic roll forming assisted laser additive manufacturing method, based on the aforementioned ultrasonic roll forming assisted laser additive manufacturing apparatus, includes the following steps: Step 1: Before starting additive manufacturing, adjust the ultrasonic incident angle θ of the ultrasonic rolling system, keep the ultrasonic amplitude rod 4 at a 30°-45° angle with the laser deposition device 2 of the laser deposition forming system, keep the ultrasonic module in the off state, adjust the ultrasonic frequency range to 20-40 kHz, and adjust the ultrasonic power range to 500-4000 W; adjust the horizontal distance L between the center of the roller 21 and the center of the laser spot of the laser deposition device 2 of the laser deposition forming system, the adjustable range of L is 10-25 mm; turn on the air pump 16, adjust the pressure regulating valve 17 to control the high pressure air pressure P, the adjustable range of P is 0.1-0.6 MPa, close the solenoid valve 18, keep the cylinder 20 in the retracted state, the stroke of the cylinder 20 is 5-20 mm; the coolant level HW in the cooling water tank 6 is 2 mm lower than the upper surface of the forming substrate 10, at this time the deposition height calibrated by the liquid level monitoring sensor 12 is 0 mm, and the liquid level height calibrated by the liquid level monitoring sensor 12 is 0 mm.

[0019] Step 2: Additive manufacturing begins. The control system 15 activates the laser deposition forming system. Powder is deposited on the forming substrate 10 along a predetermined path to form a deposition layer 8. The heat generated by the deposition layer 8 is transferred to the coolant, causing the coolant temperature to rise. When the actual temperature TS of the coolant in the cooling water tank 6 is higher than the preset temperature TP, the water chiller 13 is activated, and the coolant circulates, maintaining TS≤TP. During this period, HW remains constant. The preset temperature TP is adjusted within the range of 25-80 ℃. When the length S≥L of the deposition layer 8, the solenoid valve 18 is activated, the cylinder 20 extends, the ultrasonic generator 14 is activated, and the roller 21 presses the deposition layer 8, performing ultrasonic rolling on the deposition layer 8. The rolling length is H, and the preset single-layer deposition length is LP. When S=LP, the laser in the laser deposition forming system is turned off, while the ultrasonic rolling system and the water cooling system continue to operate. When H=LP, the ultrasonic generator 14 is turned off, the solenoid valve 18 is closed, the cylinder 20 retracts, the rolling module is raised, and the rolling module releases contact with the deposition layer 8, completing one layer deposition.

[0020] Step 3: After completing one layer of deposition, the laser deposition forming system returns to the initial point of the deposition layer 8 and raises the height HY. The single-layer deposition height is HY, and the height of the deposition layer 8 is HC. The flow rate of the water chiller 13 is increased, and the coolant level HW in the cooling water tank 6 is raised. The liquid level monitoring sensor 12 and the liquid level monitoring sensor 12 detect HC and HW in real time. During the deposition process, the relationship between HC and HW is HW = HC - 2 × HY.

[0021] Step 4: Repeat steps 2 and 3 until the deposition layer is formed.

[0022] The beneficial effects of this invention are: (1) The present invention uses the coupling effect of ultrasonic rolling and laser additive manufacturing. The rolling module adopts a threaded connection of the amplitude transformer to reduce the attenuation of the ultrasonic during the process and ensure that the ultrasonic continuously and stably acts on the molten pool. During the solidification stage of the molten pool, ultrasonic vibration is applied to disturb the molten pool, refine the grains and reduce internal defects. (2) The present invention utilizes rollers with integrated ultrasonic vibration to apply rolling pressure, and adopts a cylindrical roller structure to design the rolling module, thereby increasing the rolling area, ensuring the stability and continuity of the rolling process, and generating plastic deformation of the high-temperature plastic state material behind the molten pool, reducing residual stress, improving surface roughness, and further densifying the microstructure to improve performance.

[0023] (3) The present invention controls the temperature of the deposition layer by water cooling, reduces the impact of heat accumulation during the deposition process on the coarsening of the deposited layer after ultrasonic rolling, reduces deformation and inconsistency of the structure, and improves the overall uniformity of the formed part. Attached Figure Description

[0024] Figure 1 This is a structural diagram of an ultrasonic rolling-assisted laser additive manufacturing device according to the present invention; Figure 2 This is a structural diagram of the rolling module of an ultrasonic rolling-assisted laser additive manufacturing apparatus according to the present invention; Figure 3 Metallurgical microscope images of cross-sections of materials produced under conventional laser additive manufacturing conditions: Figure 3 (a) in the image is a metallographic microscope image of the top region section; Figure 3 (b) in the image is a metallographic microscope image of the central region section; Figure 4 Metallographic micrograph of a cross-section of a material manufactured using ultrasonic rolling-assisted laser additive manufacturing according to this invention: Figure 4 (a) in the image is a metallographic microscope image of the top region section; Figure 4 (b) in the image is a metallographic microscope image of the central region section; Figure 5 for Figure 4 (a) A magnified view of a portion at point A; Figure 6 Microhardness diagrams along the cross-sectional deposition direction for materials that have not undergone ultrasonic rolling and for materials manufactured using ultrasonic rolling-assisted laser additive manufacturing according to the present invention; 1. Support frame, 2. Laser deposition device, 3. Ultrasonic transducer, 4. Ultrasonic generator, 5. Rolling support frame, 6. Cooling water tank, 7. Deposition height monitoring sensor, 8. Deposition layer, 9. Water pipe, 10. Forming substrate, 11. Temperature sensor, 12. Liquid level monitoring sensor, 13. Water chiller, 14. Ultrasonic generator, 15. Control system, 16. Air pump, 17. Pressure regulating valve, 18. Solenoid valve, 19. Air pipe, 20. Cylinder, 21. Roller, 22. Roller shaft. Detailed Implementation

[0025] The invention will now be further described with reference to the accompanying drawings.

[0026] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0027] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0028] An ultrasonic rolling-assisted laser additive manufacturing device. For example... Figure 1 and Figure 2 As shown, it consists of a laser deposition forming system, an ultrasonic rolling system, a water cooling system, and a control system 15.

[0029] The laser deposition forming system includes a laser deposition device 2, a deposition height monitoring sensor 7, a deposition layer 8, and a forming substrate 10. The deposition height monitoring sensor 7 is fixed to the side of the cooling water tank 6 and connected to the control system 15. The liquid level monitoring sensor 12 can monitor the deposition height of the deposition layer 8 in real time and transmit the signal to the control system 15. The laser deposition device 2 is connected to the control system 15. The forming substrate 10 is fixed to the bottom surface of the cooling water tank 6. The powder or filament at the end of the laser deposition device 2 gathers on the forming substrate 10, is melted by laser, and forms the deposition layer 8 along a predetermined deposition trajectory. During the process, the height of the coolant in the cooling water tank 6 is lower than the height of the deposition layer 8 on the forming substrate 10.

[0030] The ultrasonic rolling system includes a pneumatic module, an ultrasonic module, and a rolling module, specifically: The pneumatic module includes an air pump 16, a pressure regulating valve 17, a solenoid valve 18, an air pipe 19, and a cylinder 20. The air pump 16 generates high-pressure gas, which is transmitted through the air pipe 19. The air pipe 19 is equipped with a pressure regulating valve 17 and a solenoid valve 18. The high-pressure gas passes through the pressure regulating valve 17 and the solenoid valve 18 in sequence and acts on the cylinder 20. The cylinder 20 is fixed on the bracket 1. The bracket 1 is connected to the laser deposition device 2. The pressure of the high-pressure gas output from the cylinder 20 is controlled by the pressure regulating valve 17. The solenoid valve 18 is connected to the control system 15 and is used to control the extension and retraction of the cylinder 20 to realize the movement of the ultrasonic module and the rolling module. The ultrasonic module includes an ultrasonic transducer 3, an ultrasonic amplitude transformer 4, and an ultrasonic generator 14. The top of the ultrasonic transducer 3 is connected to the cylinder 20, and the bottom of the ultrasonic amplitude transformer 4 is installed. The ultrasonic transducer 3 is connected to the control system through the ultrasonic generator 14 to realize the control of ultrasonic power, frequency, on and off. The ultrasonic waves are transmitted to the deposition layer 8 through the ultrasonic amplitude transformer 4 and the rolling module in sequence, which accelerates the flow speed of the molten pool and realizes the intervention and control of the molten pool. The rolling module includes a rolling bracket 5, a roller 21, and a roller 22. The rolling bracket 5 is fixed to the end of the ultrasonic amplitude transformer 4 by a threaded connection. The roller 22 is connected to the rolling bracket 5 by a thread to reduce ultrasonic attenuation during the process and ensure effective ultrasonic transmission. The roller 21 is cylindrical, and its circumferential surface rolls in contact with the deposition layer 8 to increase the rolling contact area. The roller 22 coaxially passes through the inside of the roller 21. The roller 21 and the roller 22 are assembled with a clearance fit, so that the roller 21 rotates by relying on the roller 22, reducing frictional resistance and ensuring the stability and continuity of the rolling process. The extension of the cylinder 20 drives the rolling module to press the deposition layer 8, so that the roller 21 and the deposition layer 8 are in close contact, generating rolling force. The ultrasonic rolling system moves synchronously with the laser deposition forming system, applying static pressure and high-frequency vibration impact force to the high-temperature area behind the molten pool of the deposition layer 8 for rolling.

[0031] The water cooling system includes a cooling water tank 6, water pipes 9, a temperature sensor 11, a liquid level monitoring sensor 12, and a water chiller 13. The temperature sensor 11 and the liquid level monitoring sensor 12 are fixed to the side of the cooling water tank 6. The temperature sensor 11 monitors the temperature of the coolant in the cooling water tank 6 in real time, and the liquid level monitoring sensor 12 monitors the liquid level of the coolant in the cooling water tank 6 in real time and transmits the signal to the control system 15. The water chiller 13 is connected to the control system 15. The control system 15 controls the water chiller 13 based on the signals fed back to the control system 15 from the temperature sensor 11 and the liquid level monitoring sensor 12, and adjusts the temperature and level of the coolant in the cooling water tank in real time through the water chiller 13.

[0032] The ultrasonic rolling-assisted laser additive manufacturing method of the present invention includes the following steps: Step 1: Before starting additive manufacturing, adjust the ultrasonic incident angle θ° of the ultrasonic rolling system, keep the ultrasonic module off, and adjust the frequency and power of the ultrasonic generator; adjust the horizontal distance L between the center of the roller 21 and the center of the laser spot of the laser deposition device 2 of the laser deposition forming system; turn on the air pump 16, adjust the pressure regulating valve 17 to control the high pressure air pressure, close the solenoid valve 18, and keep the cylinder 20 in the retracted state; the coolant level HW in the cooling water tank 6 is 2 mm lower than the upper surface of the forming substrate 10. At this time, the deposition height calibrated by the liquid level monitoring sensor 12 is 0 mm, and the liquid level height calibrated by the liquid level monitoring sensor 12 is 0 mm.

[0033] Step 2: Additive manufacturing begins. The control system 15 activates the laser deposition forming system. Powder is deposited on the forming substrate 10 according to a predetermined path to form a deposition layer 8. When the actual temperature TS of the coolant in the cooling water tank 6 is higher than the preset temperature TP, the water chiller 13 is activated, and the coolant circulates to keep TS≤TP, while HW remains constant during this period. When the length S≥L of the deposition layer 8, the solenoid valve 18 is activated, the cylinder 20 extends, the ultrasonic generator 14 is activated, and the roller 21 presses the deposition layer 8 to perform ultrasonic rolling. The rolling length is H, and the preset single-layer deposition length is LP. When S=LP, the laser in the laser deposition forming system is turned off, while the ultrasonic rolling system and the water cooling system continue to operate. When H=LP, the ultrasonic generator 14 is turned off, the solenoid valve 18 is closed, the cylinder 20 retracts, the rolling module is raised, and the rolling module releases contact with the deposition layer 8, completing one layer deposition.

[0034] Step 3: After completing one layer of deposition, the laser deposition forming system returns to the initial point of the deposition layer 8 and raises the height HY. The single-layer deposition height is HY, and the height of the deposition layer 8 is HC. The flow rate of the water chiller 13 is increased, and the coolant level HW in the cooling water tank 6 is raised. The liquid level monitoring sensor 12 and the liquid level monitoring sensor 12 detect HC and HW in real time. During the deposition process, the relationship between HC and HW is HW = HC - 2 × HY.

[0035] Step 4: Repeat steps 2 and 3 until the deposition layer is formed.

[0036] Example To enable those skilled in the art to further understand the method proposed in this invention, specific embodiments are described below. The preferred embodiments provided are for further illustrative purposes only and should not be considered as limiting the scope of the invention to the embodiments described herein, nor should they be construed as restricting the scope of protection of this invention. Non-essential improvements and adjustments made to this invention by those skilled in the art based on the above description are still within the scope of protection of this invention.

[0037] Using CoCrNi medium-entropy alloy as the research object, an ultrasonic rolling-assisted laser additive manufacturing device was used to regulate the overall microstructure uniformity and improve the performance of the material deposition layer. Specific parameters are as follows: the additive manufacturing system used was a powder-feed laser deposition system with a laser power of 650W, a scanning rate of 120 mm / min, a powder feed rate of 3.5 g / min, a HY of 0.8 mm, CoCrNi medium-entropy alloy powder, a substrate material of 316L stainless steel, substrate dimensions of 100×100×10 mm, a deposition layer height of 10 mm, an ultrasonic frequency of 20 kHz, an ultrasonic power of 1800 W, θ=30°, L=15 mm, P=0.1 MPa, TP=40 ℃, LP=100 mm, water as the coolant, and silicon nitride ceramic as the roller material.

[0038] Figure 3 Metallographic microscope images of cross-sections of materials produced under conventional laser additive manufacturing processes. Figure 4 and Figure 5 Metallographic micrographs of cross-sections of materials manufactured using ultrasonic rolling-assisted laser additive manufacturing according to this invention. Comparisons are made... Figure 4 and Figure 5 As can be seen, the CoCrNi deposited layer manufactured by ultrasonic rolling-assisted laser additive manufacturing has a deformed layer on the top layer, and the surface and sides of the deposited layer are smoother. At the same time, the porosity is reduced, indicating that ultrasonic rolling gives the material a better surface modification layer.

[0039] Figure 6 The figures show the microhardness along the depth direction of the cross-section of the CoCrNi deposited layer before and after ultrasonic rolling assisted laser additive manufacturing according to this invention. As can be seen from the figures, the CoCrNi deposited layer without ultrasonic rolling has a lower hardness along the deposition direction; the CoCrNi deposited layer manufactured using ultrasonic rolling assisted laser additive manufacturing shows a significant increase in hardness along the deposition direction, with the top layer reaching a hardness of 301.6 HV. 0.2 This indicates that ultrasonic rolling makes the overall structure of the material forming layer more uniform and improves its performance.

[0040] The above-described embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. An ultrasonic rolling-assisted laser additive manufacturing apparatus, characterized in that, The ultrasonic rolling-assisted laser additive manufacturing apparatus includes a laser deposition forming system, an ultrasonic rolling system, a water cooling system, and a control system (15). The laser deposition forming system includes a laser deposition device (2), a deposition height monitoring sensor (7), a deposition layer (8), and a forming substrate (10). The deposition height monitoring sensor (7) is fixed to the side of the cooling water tank (6) and connected to the control system (15). The deposition height monitoring sensor (7) monitors the deposition height of the deposition layer (8) in real time and transmits the signal to the control system (15). The laser deposition device (2) is connected to the control system (15). The forming substrate (10) is fixed to the bottom surface of the cooling water tank (6). The powder or filament at the end of the laser deposition device (2) gathers on the forming substrate (10), is melted by laser, and forms a deposition layer (8) along a predetermined deposition trajectory. During the process, the height of the coolant in the cooling water tank (6) is lower than the height of the deposition layer (8) on the forming substrate (10). The ultrasonic rolling system includes a pneumatic module, an ultrasonic module, and a rolling module; the pneumatic module is connected to the laser deposition device (2) and controls the movement of the ultrasonic module and the rolling module; the ultrasonic module is connected to the control system (15) and realizes intervention and control of the molten pool through the ultrasonic module; the rolling module includes a rolling support (5), a roller (21), and a roller shaft (22); the rolling support (5) is fixed to the end of the ultrasonic amplitude transformer (4), and the roller shaft (22) is connected to the rolling support (5); the roller (21) is cylindrical. Its circumferential surface rolls in contact with the deposition layer (8), and the roller (22) passes coaxially through the inside of the roller (21). The roller (21) and the roller (22) are assembled with a clearance fit, so that the roller (21) rotates on the roller (22). The retraction and extension of the cylinder (20) drive the rolling module away from and press against the deposition layer (8), so that the roller (21) and the deposition layer (8) are in close contact, generating rolling force. The ultrasonic rolling system moves synchronously with the laser deposition forming system to roll the high-temperature area behind the molten pool of the deposition layer (8). The water cooling system is connected to the control system, and adjusts the temperature and height of the coolant in the cooling water tank (6) in real time by monitoring the feedback signals.

2. The ultrasonic rolling-assisted laser additive manufacturing apparatus according to claim 1, characterized in that, The pneumatic module includes an air pump (16), a pressure regulating valve (17), a solenoid valve (18), an air pipe (19), and a cylinder (20). The air pump (16) generates high-pressure gas, which is transmitted through the air pipe (19). The air pipe (19) is equipped with a pressure regulating valve (17) and a solenoid valve (18). The high-pressure gas passes through the pressure regulating valve (17) and the solenoid valve (18) in sequence and acts on the cylinder (20). The cylinder (20) is fixed on the bracket (1). The bracket (1) is connected to the laser deposition device (2). The pressure of the high-pressure gas output from the cylinder (20) is controlled by the pressure regulating valve (17). The solenoid valve (18) is connected to the control system (15) and is used to control the extension and retraction of the cylinder (20) to realize the movement of the ultrasonic module and the rolling module.

3. The ultrasonic rolling-assisted laser additive manufacturing apparatus according to claim 2, characterized in that, The ultrasonic module includes an ultrasonic transducer (3), an ultrasonic amplitude transformer (4), and an ultrasonic generator (14). The top of the ultrasonic transducer (3) is connected to the cylinder (20), and the bottom is equipped with the ultrasonic amplitude transformer (4). The ultrasonic transducer (3) is connected to the control system (15) through the ultrasonic generator (14) to realize the control of ultrasonic power, frequency, on and off. The ultrasonic waves are transmitted to the deposition layer (8) through the ultrasonic amplitude transformer (4) and the rolling module in sequence, which accelerates the flow speed of the molten pool and realizes the intervention and regulation of the molten pool.

4. The ultrasonic rolling-assisted laser additive manufacturing apparatus according to claim 3, characterized in that, In the rolling module: the rolling bracket (5) is fixed to the end of the ultrasonic amplitude rod (4) by a threaded connection, and the roller (22) is connected to the rolling bracket (5) by a thread.

5. The ultrasonic rolling-assisted laser additive manufacturing apparatus according to claim 4, characterized in that, The water cooling system includes a cooling water tank (6), water pipes (9), a temperature sensor (11), a liquid level monitoring sensor (12), and a water chiller (13). The temperature sensor (11) and the liquid level monitoring sensor (12) are fixed to the side of the cooling water tank (6). The temperature sensor (11) monitors the temperature of the coolant in the cooling water tank (6) in real time, and the liquid level monitoring sensor (12) monitors the liquid level of the coolant in the cooling water tank (6) in real time and transmits the signal to the control system (15). The water chiller (13) is connected to the control system (15). The control system (15) controls the water chiller (13) based on the signals fed back to the control system (15) by the temperature sensor (11) and the liquid level monitoring sensor (12). The water chiller (13) adjusts the temperature and level of the coolant in the cooling water tank (6) in real time.

6. The ultrasonic rolling-assisted laser additive manufacturing apparatus according to claim 5, characterized in that, The temperature sensor (11) is a resistance temperature sensor or a thermocouple temperature sensor, and the liquid level monitoring sensor (12) and the liquid level monitoring sensor (12) are laser displacement sensors; the rolling bracket (5) and the roller (22) are made of mold steel or high temperature alloy, and the roller (21) is made of ceramic or high temperature alloy.

7. The ultrasonic rolling-assisted laser additive manufacturing apparatus according to claim 6, characterized in that, The coolant in the water-cooling system is water and a mixture of water with ethylene glycol, propylene glycol and water-cooling additives.

8. The ultrasonic rolling-assisted laser additive manufacturing apparatus according to claim 7, characterized in that, The laser deposition forming system is a powder-feeding laser deposition forming system, a wire-feeding laser deposition forming system, or a wire-powder combined laser deposition forming system.

9. A method for ultrasonic rolling-assisted laser additive manufacturing, characterized in that, Based on the ultrasonic rolling-assisted laser additive manufacturing apparatus according to any one of claims 1-8, the process includes the following steps: Step 1: Before starting additive manufacturing, adjust the ultrasonic incident angle θ of the ultrasonic rolling system, keep the ultrasonic module in the off state, and adjust the ultrasonic frequency and ultrasonic power; adjust the horizontal distance L between the center of the roller (21) and the center of the laser spot of the laser deposition device (2) of the laser deposition forming system; turn on the air pump (16), adjust the pressure regulating valve (17) to control the high pressure air pressure P, close the solenoid valve (18), and keep the cylinder (20) in the retracted state; the liquid level HW in the cooling water tank (6) is 2 mm lower than the upper surface of the forming substrate (10). At this time, the deposition height calibrated by the liquid level monitoring sensor (12) is 0 mm, and the liquid level calibrated by the liquid level monitoring sensor (12) is 0 mm. Step 2: Additive manufacturing begins. The control system (15) turns on the laser deposition forming system. Powder is deposited on the forming substrate (10) according to the predetermined path to form a deposition layer (8). The heat generated by the deposition layer (8) is transferred to the coolant, and the coolant temperature rises. When the actual temperature TS of the coolant in the cooling water tank (6) is higher than the preset temperature TP, the water chiller (13) is turned on, and the coolant circulates to keep TS≤TP. During this period, HW remains unchanged. When the length S≥L of the deposition layer (8), the solenoid valve (18) is turned on, the cylinder (20) extends, the ultrasonic generator (14) is turned on, and the roller (21) presses the deposition layer (8) to perform ultrasonic rolling on the deposition layer (8). The rolling length is H, and the preset single-layer deposition length is LP. When S=LP, the laser in the laser deposition forming system is turned off, while the ultrasonic rolling system and water cooling system continue to operate. When H=LP, turn off the ultrasonic generator (14), turn off the solenoid valve (18), the cylinder (20) retracts, the rolling module is lifted, the rolling module is released from contact with the deposition layer (8), and one layer of deposition is completed; Step 3: After completing one layer of deposition, the laser deposition forming system returns to the initial point of the deposition layer (8) and raises the height HY. The single layer deposition height is HY, and the deposition layer (8) height is HC. The flow rate of the water chiller (13) is increased, and the coolant level HW in the cooling water tank (6) is raised. The liquid level monitoring sensor (12) and the liquid level monitoring sensor (12) detect HC and HW in real time during the deposition process. Step 4: Repeat steps 2 and 3 until the deposition layer is formed.

10. The ultrasonic rolling-assisted laser additive manufacturing method according to claim 9, characterized in that, In the method: In step one: the ultrasonic incident angle θ of the ultrasonic rolling system is adjusted so that the ultrasonic amplitude rod (4) is kept at 30°-45° with the laser deposition device (2) of the laser deposition forming system; the ultrasonic frequency is adjusted in the range of 20-40 kHz, the ultrasonic power is adjusted in the range of 500-4000 W; the horizontal distance L is adjustable in the range of 10-25 mm; the high pressure P is adjustable in the range of 0.1-0.6 MPa; the stroke of the cylinder (20) is 5-20 mm. In step two: the preset temperature TP is adjusted within a range of 25-80 ℃; In the deposition process of step three, the relationship between HC and HW is HW = HC - 2 × HY.

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