Flexible follow electrode type magnetoelectric coupling laser powder feeding deposition device and method

Abstract

The application discloses a flexible follow-up electrode type magnetoelectric coupling laser powder feeding and depositing device and method. The device comprises a laser powder feeding and depositing head, a flexible follow-up contact electrode assembly, a programmable power supply, a follow-up transverse magnetic field generating device, a backflow clamp and a control unit. The flexible follow-up contact electrode assembly is arranged behind the depositing head, and the conductive contact head thereof keeps elastic conductive contact with the surface of the solidified depositing layer at the rear edge of the molten pool, so as to introduce an external current into the molten pool; the follow-up transverse magnetic field generating device is fixedly connected to the depositing head and moves synchronously, and generates a transverse magnetic field in the molten pool area, so that the current and the magnetic field are coupled to generate a Lorentz force. By switching the direct current or the alternating current, the electromagnetic braking mode and the electromagnetic oscillation mode are realized, and are respectively used for stabilizing the molten pool and promoting the epitaxial growth of single crystals / directional solidification alloys, or stirring the molten pool to refine the polycrystal structure and inhibit cracks. The application has the advantages of compact structure, convenient follow-up integration and suitability for the structure and performance regulation in the laser directional deposition process of large-size complex components.

Description

Technical Field

[0001] This invention belongs to the field of metal additive manufacturing, specifically relating to a device and method for magnetoelectric coupling control in the process of laser powder directed energy deposition (L-DED), and particularly to a flexible follower electrode type magnetoelectric coupling laser powder deposition device and method. Background Technology

[0002] Laser-guided energy deposition (LAD) is an additive manufacturing technology that uses a high-energy laser beam as a heat source and a carrier gas to simultaneously deliver metal powder into the laser-acting region. The powder is then deposited layer by layer and stacked in a molten pool on the substrate or the surface of an existing layer. This technology offers advantages such as high material utilization, flexible deposition paths, and suitability for manufacturing and repairing complex curved surfaces and large metal components. It has significant application value in aerospace, gas turbines, energy equipment, and the manufacturing and remanufacturing of key high-temperature alloy components.

[0003] However, in laser powder-fed directional energy deposition (LDED), the molten pool size is typically on the millimeter scale or even smaller, with large local temperature gradients, high cooling rates, and intense thermal cycling. This leads to strong Marangoni convection, backflow vortices, and non-equilibrium solidification behavior within the molten pool. These complex thermal-fluid coupling effects easily result in defects such as molten pool morphology fluctuations, solidification front instability, elemental segregation, porosity inclusions, and surface undulations in the deposition channel. Particularly in the additive manufacturing and repair of single-crystal or directionally solidified superalloys, excessive disturbance within the molten pool can disrupt epitaxial solidification conditions, inducing heterogeneous crystal nucleation or crystal orientation deviation, thus affecting the continuity and microstructure stability of single-crystal or directionally solidified alloys. In the deposition of polycrystalline superalloys, under rapid solidification conditions, columnar dendrites tend to grow continuously along the deposition direction and coarsen, resulting in interlayer thermal stress concentration and increased susceptibility to hot cracking. Therefore, how to achieve in-situ, stable, and controllable regulation of the flow and solidification process of the laser powder-fed molten pool is a key issue in improving the quality of deposition and the controllability of the microstructure.

[0004] Existing technologies have attempted to influence the flow of molten metal pools by applying an external magnetic field, utilizing the Lorentz force generated by the coupling of current and magnetic field within the molten pool to control the convection and solidification behavior of the molten pool. However, traditional magnetic field control methods often rely on thermocurrents induced by temperature gradients within the molten pool (i.e., weak currents based on the Seebeck thermoelectric effect), which interact with an external strong magnetic field to generate electromagnetic forces. Since these thermocurrents are relatively small (milliampere level), obtaining a Lorentz force sufficient to influence molten pool flow often requires large electromagnetic devices with magnetic field strengths exceeding 1T. Such devices are large and heavy, with some weighing several tons, and require independent water cooling and complex thermal management systems, making lightweight, integrated, and servo-driven integration with laser powder delivery deposition heads difficult. Furthermore, in complex spatial trajectories, large-sized components, and long-term continuous deposition processes, fixed large magnetic field devices are prone to mismatches between the magnetic field's effective area and the actual molten pool location, limiting their engineering applicability.

[0005] Furthermore, some existing methods introduce current into the deposition area through substrate-clamped electrodes, lateral electrodes, or external contact electrodes to enhance the electromagnetic effect. However, during laser powder deposition, the powder flow itself does not form a stable conductive channel. The morphology of the molten pool and the conductive boundary continuously change with scanning speed, powder feed rate, interlayer height, and deposition path, making it difficult to maintain a stable actual current flow path, current density distribution, and effective area. If a side electrode is directly inserted into or close to the core area of ​​the molten pool for current diversion, it can easily cause problems such as electrode ablation, molten pool contamination, increased spatter, powder feed gas flow disturbance, and instability in the deposition process, which is detrimental to the deposition and manufacturing of high-purity and high-consistency high-temperature alloys.

[0006] In existing magnetic field and current combined control schemes, the magnetic field generator and laser deposition head often lack coaxial alignment and servo-holding capabilities, and the current introduction method is mostly indirect coupling far from the molten pool. Such schemes struggle to establish a Lorentz force field within the molten pool that is well-defined in location, adjustable in intensity, controllable in direction, and repeatable. They also struggle to switch between different electromagnetic control modes within the same equipment to meet the different needs of epitaxial growth repair of single-crystal / directionally solidified alloys and refinement and shaping repair of polycrystalline structures. For example, for the manufacturing or repair of single-crystal or directionally solidified alloys, electromagnetic braking is needed to suppress excessive molten pool convection, stabilize the solidification front, and reduce the tendency for impurity crystal formation; for polycrystalline high-temperature alloys, periodic or oscillating electromagnetic action is needed to promote appropriate stirring of the molten pool, refine grains, and reduce segregation and crack sensitivity. Furthermore, existing devices still have shortcomings in terms of magnetic field servo-holding, current controllability, control mode switching capabilities, and spatial compatibility with powder feeding, protective gas, and laser optical paths.

[0007] Therefore, there is an urgent need for an electromagnetic control scheme that can stably introduce a controllable external current without intruding into the core region of the molten pool, without interfering with the powder flow and protective gas flow, and can interact structurally with a dynamically integrated magnetic field to form a Lorentz volume force field inside the laser molten pool with adjustable intensity, direction and timing. This would enable electromagnetic control of molten pool flow, solidification front stability, grain morphology and crack sensitivity, to meet different microstructure control and manufacturing repair needs, such as epitaxial growth repair of single crystal alloys and directionally solidified alloys, and polycrystalline microstructure refinement and shaping repair. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a flexible follower electrode type magnetoelectric coupling laser powder deposition device and method. It can stably inject an applied current along the solidified area behind the molten pool without allowing the electrode to enter the core area of ​​the molten pool. The flexible follower contact electrode is coupled with the follower transverse magnetic field fixed to the deposition head to form a controllable Lorentz force field inside the molten pool, thereby realizing the active control of molten pool flow, heat transfer and solidification structure.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a flexible follower electrode type magnetoelectric coupling laser powder delivery deposition device, comprising: A laser powder deposition head is used to output laser light and deliver metal powder to form a molten pool on a substrate or an existing deposited layer. A flexible follow-up contact electrode assembly is disposed behind the deposition head and moves synchronously with the deposition head. It includes a compliant connection mechanism and a conductive contact head. During the deposition process, the conductive contact head maintains elastic conductive contact with the surface of the solidified deposit layer located at the rear edge of the molten pool to introduce an applied current into the molten pool region. A follow-up transverse magnetic field generator is fixed to the deposition head and moves synchronously with the deposition head. It is used to generate a transverse magnetic field in the molten pool region. The direction of the magnetic induction lines of the transverse magnetic field is perpendicular to the direction of the deposition scanning path. A programmable power supply, electrically connected to a flexible follower contact electrode assembly, is used to output DC or AC current, and its current mode is switchable. The reflow fixture is electrically connected to the return terminal of the programmable power supply and conductively connected to the substrate or tooling fixture to form a closed current loop through the conductive contact head, deposited layer, molten pool area, substrate to the reflow fixture; The control unit is connected to the laser powder delivery and deposition head, the programmable power supply, and the follow-up magnetic field generator, respectively, and is used to coordinate the adjustment of laser power, powder delivery rate, deposition scanning rate, current parameters, and magnetic field parameters.

[0011] The interaction between the applied current and the transverse magnetic field in the molten pool region generates Lorentz force, which regulates the flow, heat transfer and solidification behavior of the molten pool.

[0012] In one embodiment, the conductive contact head is a flexible brush, which is a carbon brush, a metal fiber brush, or a composite conductive brush; the compliant connection mechanism is a constant force spring, a pneumatic constant pressure mechanism, a hydraulic constant pressure mechanism, or a counterweight constant force mechanism, used to apply constant pressure to the flexible brush so that it maintains sliding contact with the solidified deposited layer surface at the rear edge of the molten pool.

[0013] In one embodiment, the conductive contact head is a conductive roller whose outer surface is made of tungsten copper alloy, beryllium copper alloy or silver graphite material. It is pressed against the surface of the solidified deposited layer by a compliant connection mechanism and rolls along the deposition path to maintain contact.

[0014] Preferably, the distance between the conductive contact head and the rear edge of the molten pool is 10-30 mm. When a flexible brush is used, its front end is in close contact with the partially solidified molten zone surface at the rear edge of the molten pool, and is moved back about 20 mm from the laser action point; when a roller electrode is used, the contact point is moved back about 20 mm relative to the molten pool.

[0015] Preferably, the programmable power supply outputs a DC current of 20-50A and an effective AC current of 20-50A with a frequency of 50-100Hz. The follow-up magnetic field generator is an electromagnetic coil that uses DC excitation to form a transverse magnetic field with a magnetic induction intensity of 0.05-0.1T. The compliant connection mechanism provides a constant contact pressure to the conductive contact head during the deposition process, allowing the conductive contact head to automatically adapt to changes in the workpiece surface height.

[0016] Preferably, the control unit can programmably set the waveform, frequency and amplitude of the output current of the programmable power supply, and coordinately control the laser power, powder feeding rate, deposition scanning rate, gas flow rate and magnetic field strength, and dynamically adjust the intensity and mode of the Lorentz force in the molten pool during the deposition process.

[0017] Secondly, the present invention provides a flexible follower electrode type magnetoelectric coupling laser powder deposition method, which is implemented using the above-mentioned device and includes the following steps: The follow-up magnetic field generator is activated to generate a transverse magnetic field in the molten pool area, with the direction of the magnetic induction lines perpendicular to the direction of the deposition scanning path; Laser-driven powder-directed energy deposition is performed to form a molten pool that moves with the scan on the substrate or the already deposited layer; The conductive contact head of the flexible follower contact electrode assembly maintains elastic conductive contact with the solidified deposited layer surface at the rear edge of the molten pool. An applied current is introduced into the molten pool area through the conductive contact head by a programmable power supply, forming a closed current loop through the conductive contact head, deposited layer, molten pool area, substrate to the reflow fixture. During the deposition scanning process, the applied current and the transverse magnetic field are coupled in the molten pool to generate Lorentz force, which regulates the flow, heat transfer and solidification behavior of the molten pool.

[0018] Furthermore, when the programmable power supply outputs DC current, it executes the electromagnetic braking mode. The DC current couples with the transverse magnetic field to generate a steady-state Lorentz force, which suppresses Marangoni convection in the molten pool, stabilizes the solidification interface, promotes epitaxial growth, and suppresses the generation of impurities. This is used for the deposition or repair of single-crystal or directionally solidified alloys. When the programmable power supply outputs AC current, it executes the electromagnetic oscillation mode. The AC current couples with the transverse magnetic field to generate an alternating Lorentz force, which induces forced oscillation of the molten pool, breaks dendrites, promotes the transformation of columnar crystals to equiaxed crystals, and suppresses solidification cracking caused by element segregation and thermal stress concentration. This is used for the deposition or repair of polycrystalline alloys.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects: 1. This invention establishes a stable ohmic contact at the trailing edge of the molten pool using a flexible, follow-up contact electrode, and guides the injection of applied current. This prevents the electrode from intruding into the core area of ​​the molten pool, reducing the risk of contamination and ablation, and improving the stability of long-term continuous deposition. Furthermore, compared to open-arc discharge current diversion, direct conductivity via the flexible contact electrode avoids interference from arc light and high-frequency arc ignition, ensuring the stability of the laser molten pool. The device of this invention has a simple structure and strong adaptability. The flexible brush or roller electrode can be followed and clamped by a simple mechanical mechanism, and the electromagnetic coil can be easily installed near the deposition head without affecting the movement and operation of the equipment. The system can achieve constant current and constant magnetic output without complex sensor control, resulting in high reliability. The flexible electrode can adapt to curved trajectories and uneven surfaces, accommodating deposition paths of different shapes and ensuring isotropic electromagnetic interaction effects.

[0020] 2. This invention forms a controllable Lorentz force field in the molten pool by "applied current + follow-up transverse magnetic field". Usable volume force can be obtained under a moderate magnetic field strength of 0.05~0.1T, which reduces the volume, mass and thermal management complexity of the magnetic field system, and facilitates integrated follow-up with the deposition head, and is suitable for deposition of complex trajectories and large-sized components.

[0021] 3. The same device of this invention achieves dual modes of electromagnetic braking and electromagnetic oscillation by switching the current type, which are respectively applicable to the epitaxial growth stabilization of single-crystal / directionally solidified alloys and the grain refinement and crack suppression of polycrystalline alloys, realizing multiple uses in one machine. In electromagnetic braking mode, it suppresses molten pool convection and morphological fluctuations, which is beneficial to the epitaxial solidification stability of single-crystal / directionally solidified alloys and reduces the tendency of impurity crystals; in electromagnetic oscillation mode, it induces forced oscillation / stirring, realizes dendrite shearing and microstructure refinement, which is beneficial to the grain refinement of polycrystalline high-temperature alloys and reduces the tendency of crack formation.

[0022] 4. This invention features long-term continuous deposition capability. The flexible brush or roller electrode can operate stably for extended periods, and with the continuous action of the follow-up magnetic field, it is suitable for additive manufacturing and repair of large-size metal components. Compared to methods such as mechanical vibration, which are prone to failure due to thermal fatigue or wear, this invention is more conducive to long-term continuous deposition, with good process stability, high forming efficiency, and engineering feasibility and industrial application value.

[0023] In summary, this invention achieves active magneto-electric composite control of the laser-directed energy deposition molten pool by integrating a flexible follower electrode and an electromagnetic field device. This technology can target and control the flow and solidification process of the molten pool, thereby autonomously texturing crystal orientation. Ultimately, it can significantly improve the microstructure and properties of high-value metal components in deposition manufacturing and repair, demonstrating clear engineering application value. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the flexible follower electrode type magnetoelectric coupling laser powder delivery and deposition device according to an embodiment of the present invention; Figure 2 This is a partial structural schematic diagram of the flexible follower brush contact electrode assembly in an embodiment of the present invention; Figure 3 This is a schematic diagram of the flexible roller contact electrode assembly in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the effect of Lorentz force in the molten pool under DC electromagnetic braking mode in an embodiment of the present invention. Figure 5 This is a schematic diagram illustrating the effect of Lorentz oscillation force in the molten pool under AC electromagnetic oscillation mode in an embodiment of the present invention.

[0025] Explanation of reference numerals in the attached figures: 1-Laser directed energy deposition head; 2-Powder nozzle; 3-Molten pool; 4-Deposited layer; 5-Flexible follow-up contact electrode assembly; 6-Conductive contact head; 7-Electromagnetic coil; 8-Reflow fixture; 9-Substrate; 21-Scanning direction; 51-Constant force spring; 61-Flexible brush; 62-Conductive roller; 63-Roller support. Detailed Implementation

[0026] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0027] The present invention is described below through specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] like Figures 1-5 As shown, the flexible follower electrode type magnetoelectric coupling laser powder delivery deposition device provided in this embodiment of the invention includes: a laser powder delivery deposition head, a flexible follower contact electrode assembly 5, a follower transverse magnetic field generator, a programmable power supply, a return fixture 8, and a control unit.

[0029] The laser powder deposition head includes a laser-directed energy deposition head 1, a powder nozzle 2, and a laser. The laser-directed energy deposition head 1 is connected to the laser via an optical fiber and is used to output laser light and form a molten pool 3 on the surface of the substrate 9. The powder nozzle 2 is located below the laser-directed energy deposition head 1 and is used to feed metal powder into the molten pool 3 to achieve layer-by-layer deposition. The laser-directed energy deposition head 1 moves along the scanning direction 21, and the molten pool 3 moves synchronously with the laser-directed energy deposition head 1.

[0030] The flexible follower contact electrode assembly 5 is arranged behind the laser powder feeding deposition head, and is fixedly connected to the laser directional energy deposition head 1 via a bracket and moves synchronously with it. In this embodiment, the flexible follower contact electrode assembly 5 is positioned approximately 20 mm behind the center of the laser molten pool via the bracket. The flexible follower contact electrode assembly 5 includes a compliant connection mechanism and a conductive contact head 6. During the deposition process, the compliant connection mechanism provides a constant contact pressure to the conductive contact head 6, allowing the conductive contact head 6 to automatically adapt to changes in the workpiece surface height. During the deposition process, the conductive contact head 6 maintains elastic conductive contact with the surface of the solidified deposition layer 4 located at the rear edge of the molten pool 3. The compliant connection mechanism can be a constant force spring, a pneumatic constant pressure mechanism, a hydraulic constant pressure mechanism, or a counterweight constant force mechanism; in this embodiment, a constant force spring 51 is used.

[0031] like Figure 2As shown, this is a partially enlarged schematic diagram of the flexible follower brush contact electrode assembly. In the figure, the conductive contact head 6 is a flexible brush structure. The flexible brush 61 is composed of a carbon brush, a metal fiber brush, or a composite conductive brush. A constant downward pressure is applied by a constant force spring 51, causing the end of the flexible brush 61 to maintain sliding contact with the surface of the solidified deposited layer 4 at the rear edge of the molten pool, forming a stable elastic conductive contact. This allows a vertically downward applied current to be injected into the molten pool region. Figure 2 (The black arrow in the middle indicates the direction of current). By maintaining constant pressure, the flexible brush 61 can maintain a basically constant contact pressure even under conditions of high fluctuation on the deposition layer surface, thermal deformation, or splash adhesion, thereby reducing contact resistance fluctuations and improving the stability of long-term continuous deposition.

[0032] In this embodiment of the invention, the flexible brush 61 is composed of a brush bundle made of multiple strands of highly conductive carbon fiber or copper alloy wire, possessing excellent durability and enabling continuous and stable conductivity over a long period. One end of the brush bundle is fixed to the brush holder, while the other end rests against the surface of the molten pool in a free-flowing bristle shape. The brush holder is hinged to a support via a pivot and connected to one end of a constant-force spring. The other end of the constant-force spring is fixed to the deposition head support, thereby applying a constant downward elastic force to the flexible brush, ensuring that the bristle tips remain in close contact with the molten pool surface even when encountering unevenness on the workpiece surface. To maintain optimal contact, the brush extension length can be fine-tuned or the brush bundle replaced approximately every 4 hours of deposition. The start, stop, and magnitude of the applied current can be programmed and set through the control system, allowing for on-demand application at different stages of deposition and precise control over the key deposited layer structure. After laser deposition stops, the current is automatically cut off, ensuring safety and controllability throughout the entire process.

[0033] In this embodiment of the invention, the flexible brush 61 is 10-30 mm (preferably 20 mm) away from the rear edge of the molten pool, forming an elastic ohmic contact with the surface of the deposition layer 4, so as to achieve stable injection of applied current while avoiding entry into the core area of ​​the high-temperature molten pool.

[0034] In another embodiment, such as Figure 3 The diagram shows a schematic of the flexible roller contact electrode assembly. In the diagram, the conductive contact head 6 is a conductive roller structure. The outer surface of the conductive roller 62 is made of high-temperature resistant conductive materials such as tungsten copper alloy, beryllium copper alloy, or silver graphite. The conductive roller 62 is connected to a compliant connection mechanism (constant force spring 51) via a roller bracket 63. The constant force spring 51 presses the conductive roller 62 firmly against the surface of the solidified deposition layer 4, allowing it to roll along the deposition path to maintain conductive contact. The conductive roller 62 is also positioned 10-30 mm behind the molten pool to achieve stable current injection. Figure 3(The black arrow in the middle indicates the direction of current). Additionally, the programmable power supply is connected to the conductive roller 62 via wires and a slip ring device. When the laser-directed energy deposition head 1 moves, the conductive roller 62 rolls forward under spring pressure, closely adhering to the surface of the newly formed deposition layer behind the molten pool, maintaining electrical contact with the solidified deposition layer 4 at all times, and continuously introducing current into the tail region of the molten pool. Because the conductive roller 62 is rollable, its friction relative to the workpiece is relatively small, avoiding the brush wear problem associated with brushes. Therefore, it is suitable for long-term deposition processes, especially in cases where the deposition path is straight or has smooth bends, maintaining stable contact and low loss. Even if the deposition path has bends or surface undulations, the conductive roller 62, under the compliant action of the spring mechanism, can promptly adjust its angle to follow surface changes, maintaining reliable contact and uninterrupted power supply.

[0035] like Figure 1 As shown, the follow-up transverse magnetic field generator is an electromagnetic coil 7, which is fixed to the laser-directed energy deposition head 1 and moves synchronously with the laser-directed energy deposition head 1 to generate a transverse magnetic field in the molten pool 3 region. The electromagnetic coil 7 uses DC excitation to form a constant transverse magnetic field B, and the direction of the magnetic induction lines is perpendicular to the direction of the deposition scanning path (e.g., ...). Figure 4 , Figure 5 The direction of the magnetic field B is shown in the diagram, forming a follow-up transverse magnetic field with a magnetic induction intensity of 0.05~0.1T. For ease of description of the directional relationship, the movement direction of the deposition head is defined as the scanning direction 21 (i.e., the deposition path direction). When the laser-directed energy deposition head 1 moves along the X-axis for deposition, the magnetic field B generated by the electromagnetic coil 7 points along the Y-axis (horizontal direction). In this embodiment of the invention, measurements show that the magnetic induction intensity at the melt pool 3 is approximately 0.05 T. Therefore, a magnetic field B perpendicular to the current I exists within the melt pool 3, according to the Lorentz force F... L The principle of I×B will generate a Lorentz force F inside the molten pool of conductive metal. L This is to regulate the flow, heat transfer, and solidification behavior of the molten pool.

[0036] A programmable power supply, electrically connected to a flexible follower contact electrode assembly, is used to output DC or AC current, and its current mode is switchable. By controlling the programmable power supply, the DC / AC output and its amplitude, frequency, and other parameters can be switched to achieve electromagnetic braking mode or electromagnetic oscillation mode. In this embodiment of the invention, the DC current output by the programmable power supply is 20~50A; the effective value of the output AC current is 20~50A, and the frequency is 50~100Hz.

[0037] The return fixture 8 is clamped to the substrate 9 or a tooling fixture and is electrically connected to the substrate 9 or the tooling fixture; simultaneously, it is electrically connected to the return circuit terminal of the programmable power supply. The positive terminal of the programmable power supply is electrically connected to the conductive contact head 6, forming a closed current loop through the conductive contact head 6, the deposition layer 4, the molten pool 3 region, the substrate 9, and the return fixture 8. Since the resistance of the liquid molten pool is less than that of the solid substrate, the applied current preferentially flows through the molten pool 3 region, then is conducted to the substrate 9 below, and finally flows into the return circuit terminal of the programmable power supply through the return fixture 8 (clamped in the substrate), thus forming a closed current loop and achieving the purpose of introducing applied current into the molten pool region. In one specific embodiment, the conductive contact head 6 is connected to a programmable power supply via a wire. When the laser directional energy deposition head 1 moves to perform deposition, the flexible brush 61, under the action of the constant force spring 51, moves to adhere to the surface of the deposited layer, ensuring that the brush bristles are always in contact with the tail region of the solidified molten pool. The applied current is introduced into the deposited layer 4 through the conductive contact head 6 and flows to the molten pool 3, and then returns to the return end of the programmable power supply circuit via the substrate 9 and the return fixture 8, forming a closed loop. Since the brush always maintains physical contact and the programmable power supply output is in constant current mode, the current loop does not cross the air or protective gas gap during the deposition movement. The current in the molten pool 3 is stable and controlled, and there is no ionizing arc generation, thus avoiding unwanted discharge phenomena and improving circuit stability.

[0038] The control unit is connected to the laser directional energy deposition head 1, the programmable power supply and the electromagnetic coil 7 respectively, and is used to coordinate the adjustment of laser power, powder feeding rate, deposition scanning rate, current parameters and magnetic field parameters.

[0039] The flexible follower electrode type magnetoelectric coupling laser powder delivery deposition device of the present invention provides two operating modes: Electromagnetic braking mode (DC + transverse magnetic field): such as Figure 4 As shown, during the deposition process, when the programmable power supply outputs a DC current I, the DC current is injected through the conductive contact head 6 from the surface of the solidified deposited layer 4, flows through the molten pool 3 region, and then returns to the programmable power supply circuit return terminal via the substrate 9 and the return fixture 8. The DC current interacts with the transverse magnetic field (direction perpendicular to the scanning direction) generated by the electromagnetic coil 7, producing a steady-state Lorentz force F in a constant direction within the molten pool 3. L (like Figure 4 As shown, the black arrow indicates the direction of the Lorentz force. This Lorentz force provides electromagnetic damping to the Marangoni convection driven by the surface tension gradient within the molten pool, suppressing disordered flow and eddies in the molten pool. This stabilizes the temperature gradient and solidification interface within the molten pool, achieving an electromagnetic braking mode. This is suitable for the deposition forming or repair of single-crystal or directionally solidified high-temperature alloys, promoting the stability of the epitaxial solidification process and reducing the tendency for impurity crystal formation.

[0040] Electromagnetic oscillation mode (AC + transverse magnetic field): such as Figure 5As shown, when the programmable power supply switches, the output AC current I... AC When the direction of the applied current alternates periodically with time, it couples with the transverse magnetic field to generate a periodically changing Lorentz oscillating force. This alternating Lorentz force drives the molten metal in the pool to produce forced oscillations and periodic shear flow (e.g., Figure 5 (As shown by the black arrow in the middle), it can effectively break up growing primary dendrites, sever dendrite arms and promote the formation of new crystal nuclei, promote the transformation of columnar crystals into equiaxed crystals, realize electromagnetic oscillation mode, and is suitable for the deposition forming or repair of polycrystalline high-temperature alloys to promote grain refinement and reduce the tendency of crack formation.

[0041] This invention also provides a flexible follower electrode type magnetoelectric coupling laser powder deposition method, implemented using the above-mentioned device, including the following steps: The follow-up transverse magnetic field generator is activated: the electromagnetic coil 7 is activated by the control unit, and a DC excitation current is applied to generate a transverse magnetic field in the molten pool 3 region. The magnetic induction lines of the transverse magnetic field are perpendicular to the deposition scanning path direction, and the magnetic induction intensity is 0.05~0.1T. This magnetic field is established before deposition begins and continuously covers the molten pool region throughout the entire deposition process.

[0042] Laser powder deposition initiation: The laser is activated, outputting laser light through the laser-directed energy deposition head 1, while simultaneously delivering metal powder to the substrate surface through the powder nozzle 2, forming a molten pool 3 on the substrate or existing deposited layer that moves with the scan. The powder delivery and gas management components simultaneously supply carrier gas and protective gas to the deposition area to maintain stable powder beam convergence.

[0043] Establishing an elastic conductive contact for the flexible follower electrode: The conductive contact head 6 of the flexible follower electrode assembly 5 maintains elastic conductive contact with the surface of the solidified deposited layer 4 along the rear edge of the molten pool 3. The conductive contact head 6 applies a constant contact pressure via a compliant connection mechanism (such as a constant force spring), ensuring it remains pressed firmly against the deposited layer surface throughout the deposition process and automatically adapts to changes in workpiece surface height. The distance between the conductive contact head 6 and the rear edge of the molten pool 3 is 10~30mm, preferably 20mm. The flexible follower electrode assembly 5 moves synchronously with the laser-directed energy deposition head 1.

[0044] An external current is introduced to form a closed loop: The programmable power supply is activated by the control unit, and an external current is introduced into the molten pool 3 region through the conductive contact head 6 and the solidified deposit layer 4. The external current forms a closed current loop through "conductive contact head 6—deposit layer 4—molten pool 3 region—substrate 9—return fixture 8". Since the resistance of the liquid molten pool is less than that of the solid substrate, the external current automatically flows preferentially from the contact head through the deposit layer to the molten pool region.

[0045] Current mode selection based on material and microstructure objectives: The applied current mode is selected via the control unit based on the alloy material to be processed and the microstructure objectives. When the material is a single crystal or a directionally solidified alloy, select the DC power mode (electromagnetic braking mode). In this mode, the programmable power supply outputs a DC current (20~50A). The DC current couples with the transverse magnetic field to generate a steady-state Lorentz force, which electromagnetically dampens the convection flow in the molten pool, suppresses Marangoni convection, stabilizes the solidification interface, thereby promoting the stability of the epitaxial solidification process and reducing the tendency for impurity crystal formation.

[0046] When the material is polycrystalline or requires grain refinement, select the AC mode (electromagnetic oscillation mode). In this mode, the programmable power supply outputs AC current (RMS 20~50A, frequency 50~100Hz). The AC current couples with the transverse magnetic field to generate alternating Lorentz force, inducing forced oscillation or periodic stirring of the molten pool, which has a shearing and disturbance effect on dendrite growth, thereby promoting grain refinement and improving the uniformity of solidification structure.

[0047] Dynamic control during deposition: During the deposition scanning process, the control unit coordinates and adjusts the laser power, powder feed rate, deposition scanning rate, current parameters (magnitude and polarity of DC, effective value of AC, frequency and waveform characteristics), and magnetic field parameters in real time to dynamically adjust the intensity and mode of the Lorentz force within the molten pool. After deposition, the control unit cuts off the current and shuts off the magnetic field or maintains the magnetic field until the molten pool solidifies.

[0048] The following specific embodiments illustrate the flexible follower electrode type magnetoelectric coupling laser powder delivery deposition device and method of the present invention.

[0049] Example 1: Repair of René N5 monocrystalline blades (brush type + electromagnetic braking mode) In this embodiment, René N5 single-crystal blades were selected as the repair target, and René N5 alloy powder (particle size 53~150 μm) with a composition matching the matrix was used. The area to be repaired was polished, degreased, and dried before deposition. Figure 1The apparatus shown is used for repair deposition. The laser power is 800~1600 W (preferably 800~1200 W); the laser spot diameter is 1.0~1.5 mm (preferably 1.5 mm); the powder feed rate is 4~10 g / min (preferably 6 g / min); and the deposition scanning rate is 300~800 mm / min (preferably 600 mm / min). Argon is used for both the carrier gas and the protective gas, with a carrier gas flow rate of 2~5 L / min (preferably 3 L / min) and an outer protective gas flow rate of 8~15 L / min (preferably 10 L / min). The conductive contact head uses a flexible brush, positioned 20 mm behind the molten pool, and maintains elastic ohmic contact with the solidified deposition layer surface via a constant force spring. The programmable power supply outputs a DC current of 40~50A. The servo transverse magnetic field strength is 0.06~0.08T, and its direction is perpendicular to the scanning direction.

[0050] During deposition, the applied DC current couples with the steady-state transverse magnetic field, forming a stable Lorentz braking force field within the molten pool. This suppresses Marangoni convection and backflow eddies, reduces surface fluctuations in the molten pool, and stabilizes the solid-liquid interface morphology. Simultaneously, the stable DC current helps maintain the continuity of the molten pool's thermal flow field and the solidification front, reducing the retention of inclusion bubbles and porosity in the deposited layer. The specific steps of this embodiment are as follows: First, the electromagnetic coil 7 is activated to generate a 0.06~0.08T transverse magnetic field; then, the laser and powder feeding system are activated to form a molten pool 3 on the surface of the René N5 single-crystal blade; subsequently, the flexible brush-type conductive contact head 6 maintains elastic contact with the surface of the solidified deposited layer 4 approximately 20mm behind the molten pool 3; a 40~50A DC current is output through a programmable power supply to form a closed loop; during the deposition scanning process, the DC current couples with the transverse magnetic field to generate a steady-state Lorentz force, continuously suppressing molten pool convection; the current is cut off after deposition is completed. The repair results show that the repaired area maintains continuous epitaxial growth with the René N5 single crystal matrix, the tendency for the formation of impurities and low-angle grain boundaries is reduced, and the solidification structure of the deposited layer is more straight and continuous.

[0051] Example 2: Deposition of IN718 polycrystalline superalloy (roller type + electromagnetic oscillation mode) In this embodiment, IN718 alloy powder is used for multi-pass, multi-layer laser-fed directional energy deposition on a nickel-based alloy substrate. The powder particle size is 53–150 μm. The laser power is 1000–1800 W (preferably 1400 W); the laser spot diameter is 1.5–3.0 mm (preferably 2.0 mm); the powder feed rate is 6–14 g / min (preferably 8 g / min); and the deposition scanning rate is 400–1000 mm / min (preferably 700 mm / min). Argon is used as the carrier gas, with a flow rate of 3–6 L / min (preferably 4.5 L / min). The outer protective gas is argon or an argon-helium mixture, with a flow rate of 10–20 L / min (preferably 15 L / min). The conductive contact head is a conductive roller with an outer surface of tungsten-copper alloy, positioned 20 mm behind the molten pool, maintaining elastic ohmic contact with the solidified deposition layer. The programmable power supply outputs AC current with an effective value of 45~50A and a frequency of 50~100Hz. The servo transverse magnetic field strength is 0.06~0.08T, and its direction is perpendicular to the scanning direction.

[0052] During deposition, alternating Lorentz forces induce periodic shearing and forced oscillations in the molten pool, promoting the fragmentation of columnar dendrites, the formation of equiaxed crystals, and solute homogenization, thereby reducing segregation, porosity, and solidification cracking tendency in the IN718 polycrystalline deposition layer. The specific steps of this embodiment are as follows: First, an electromagnetic coil 7 is activated to generate a 0.06~0.08T transverse magnetic field; then, the laser and powder feeding system are activated to form a molten pool 3 on the nickel-based alloy substrate; subsequently, a roller-type conductive contact head 6 maintains elastic rolling contact with the surface of the solidified deposition layer 4 approximately 20mm behind the molten pool 3; an alternating current is output through a programmable power supply to form a closed loop; during the deposition scanning process, the alternating current couples with the transverse magnetic field to generate periodic Lorentz oscillation forces, continuously inducing forced oscillations in the molten pool; the current is cut off after deposition. The post-deposition microstructure shows that the columnar crystals are broken up, the proportion of equiaxed crystals is significantly increased, the grains are refined, and there are no cracks or visible pores.

[0053] Example 3: Implementation of Wire Feeding Method In any of the above embodiments, the laser powder deposition apparatus can also supply the filler material by wire feeding. In this embodiment, IN718 alloy wire is selected for laser wire feeding directional energy deposition, with a wire diameter of 0.8~1.2 mm, preferably 1.0 mm. The laser power is 1000~2500W, preferably 1500W; the laser spot diameter is 1.0~2.0 mm, preferably 1.5 mm; the wire feeding speed is 0.6~3.0 m / min, preferably 1.2 m / min; and the deposition scanning rate is 300~900 mm / min, preferably 600 mm / min. Argon is used as the protective gas, with a flow rate of 10~20 L / min, preferably 15 L / min.

[0054] In this embodiment, a wire feeding channel and a wire feeding mechanism are provided on the laser directional energy deposition head 1. The wire feeding channel can be located at the central axis of the deposition head, and its outlet end extends to the top of the molten pool 3 or the leading edge region of the molten pool 3. The metal wire is continuously fed into the molten pool 3 by the wire feeding mechanism through the wire feeding channel. The wire feeding channel and the flexible follower contact electrode assembly 5 are spatially separated, so that the wire feeding path does not interfere with the elastic conductive contact between the conductive contact head 6 and the solidified deposition layer 4 at the rear edge of the molten pool 3, and at the same time, the conductive contact head 6 does not block the wire feeding path.

[0055] During deposition, the applied current, supplied by a programmable power supply, is injected into the solidified deposited layer 4 and the molten pool 3 region via the conductive contact head 6. This current couples with the transverse magnetic field to generate a Lorentz force, thereby regulating the flow, heat transfer, and solidification behavior of the molten pool. Depending on the material type and desired microstructure, either an electromagnetic braking mode or an electromagnetic oscillation mode can be selected. The filament and powder can be used individually or in combination. Combination refers to simultaneous filament and powder feeding, with the filament serving as the primary filler material and the powder supplementing the composition for fine-tuning or functional enhancement.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various modifications and variations can be made to the embodiments 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 protection scope of the present invention.

Claims

1. A flexible follower electrode type magnetoelectric coupling laser powder delivery deposition device, characterized in that, include: A laser powder deposition head is used to output laser light and deliver metal powder to form a molten pool on a substrate or an existing deposited layer. A flexible follower contact electrode assembly is disposed behind the deposition head and moves synchronously with the deposition head. The flexible follower contact electrode assembly includes a compliant connection mechanism and a conductive contact head. During the deposition process, the conductive contact head maintains elastic conductive contact with the surface of the solidified deposited layer located at the rear edge of the molten pool to introduce an applied current into the molten pool region. A follow-up transverse magnetic field generator is fixed to the deposition head and moves synchronously with the deposition head to generate a transverse magnetic field in the molten pool region. The direction of the magnetic induction lines of the transverse magnetic field is perpendicular to the direction of the deposition scanning path. A programmable power supply, electrically connected to the flexible follower contact electrode assembly, is used to output DC current or AC current, and its current mode can be switched. The reflow fixture is electrically connected to the return terminal of the programmable power supply and conductively connected to the substrate or tooling fixture to form a closed current loop through the conductive contact head, the deposited layer, the molten pool area, the substrate and the reflow fixture. The control unit is connected to the laser powder delivery and deposition head, the programmable power supply, and the follow-up magnetic field generator, respectively, and is used to coordinate the adjustment of laser power, powder delivery rate, deposition scanning rate, current parameters, and magnetic field parameters. The applied current and the transverse magnetic field interact in the molten pool region to generate Lorentz force, thereby regulating the flow, heat transfer and solidification behavior of the molten pool.

2. The apparatus according to claim 1, characterized in that: The conductive contact head is a flexible brush, which can be a carbon brush, a metal fiber brush, or a composite conductive brush; the compliant connection mechanism is a constant force spring, a pneumatic constant pressure mechanism, a hydraulic constant pressure mechanism, or a counterweight constant force mechanism, used to apply a constant pressure to the flexible brush so that it maintains sliding contact with the solidified deposited layer surface at the rear edge of the molten pool.

3. The apparatus according to claim 1, characterized in that: The conductive contact head is a conductive roller, the outer surface of which is made of tungsten copper alloy, beryllium copper alloy or silver graphite material; the conductive roller is pressed against the surface of the solidified deposited layer by a compliant connection mechanism and rolls along the deposition path to maintain contact.

4. The apparatus according to claim 1, characterized in that: The distance between the conductive contact and the rear edge of the molten pool is 10~30mm.

5. The apparatus according to claim 1, characterized in that: The programmable power supply outputs a DC current of 20~50A; the effective value of the AC current output by the programmable power supply is 20~50A, and the frequency is 50~100Hz.

6. The apparatus according to claim 1, characterized in that: The follow-up transverse magnetic field generator is an electromagnetic coil, which uses DC excitation to form a transverse magnetic field with a magnetic induction intensity of 0.05~0.1T.

7. The apparatus according to claim 1, characterized in that: The compliant connection mechanism provides a constant contact pressure to the conductive contact head during the deposition process, enabling the conductive contact head to automatically adapt to changes in the height of the workpiece surface.

8. The apparatus according to claim 1, characterized in that: The control unit can programmatically set the waveform, frequency and amplitude of the output current of the programmable power supply, and coordinately control the laser power, powder feeding rate, deposition scanning rate, gas flow rate and magnetic field strength, and dynamically adjust the intensity and mode of the Lorentz force in the molten pool during the deposition process.

9. A flexible follower electrode type magnetoelectric coupling laser powder deposition method, implemented using the apparatus described in any one of claims 1 to 8, characterized in that, Includes the following steps: The follow-up transverse magnetic field generator is activated to generate a transverse magnetic field in the molten pool region. The direction of the magnetic induction lines of the transverse magnetic field is perpendicular to the direction of the deposition scanning path. Laser-driven powder-directed energy deposition is performed to form a molten pool that moves with the scan on the substrate or the already deposited layer; The conductive contact head of the flexible follower contact electrode assembly maintains elastic conductive contact with the solidified deposited layer surface at the rear edge of the molten pool. An applied current is introduced into the molten pool area through the conductive contact head by a programmable power supply, forming a closed current loop through the conductive contact head, deposited layer, molten pool area, substrate to the reflow fixture. During the deposition scanning process, the applied current and the transverse magnetic field are coupled in the molten pool to generate Lorentz force, thereby regulating the flow, heat transfer and solidification behavior of the molten pool.

10. The method according to claim 9, characterized in that: When the programmable power supply outputs DC current, it executes the electromagnetic braking mode. The DC current couples with the transverse magnetic field to generate a steady-state Lorentz force, which suppresses Marangoni convection in the molten pool, stabilizes the solidification interface, and realizes impurity-free epitaxial growth in the deposition / repair process of single crystal or directional solidification alloys. When the programmable power supply outputs AC current, it executes the electromagnetic oscillation mode. The AC current couples with the transverse magnetic field to generate an alternating Lorentz force, which induces forced oscillation of the molten pool, breaks dendrites and promotes the transformation of columnar crystals to equiaxed crystals, thereby realizing grain refinement and crack suppression in the deposition or repair process of polycrystalline alloys.

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