A coaxial tungsten electrode conductive type magneto-electric coupling laser powder feeding deposition device and method

Abstract

The application discloses a coaxial tungsten electrode conductive magneto-electric coupling laser powder feeding deposition device and method. The device comprises a laser powder feeding deposition head, a coaxially arranged tungsten needle electrode, a programmable power supply, a transverse magnetic field generating unit, a powder feeding and gas management assembly, a backflow clamp and a control unit. A micro-beam plasma arc is generated between the tungsten needle electrode and a workpiece, and controllable direct current or alternating current is injected into a molten pool; a follow-up transverse magnetic field is coupled with the current to generate a Lorentz force field in the molten pool. By switching the current mode, two kinds of regulation and control are realized: an electromagnetic braking mode of direct current and magnetic field coupling, which suppresses the convection of the molten pool and promotes the single crystal / directional solidification alloy epitaxial growth without impurities; and an electromagnetic oscillation mode of alternating current and magnetic field coupling, which stirs the molten pool, shears the dendrites, refines the polycrystalline structure and suppresses cracks. The application has a compact structure and is convenient for follow-up integration, and is suitable for the regulation and control of the structure and performance 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 magnetoelectric coupling active control device and method for the laser powder-directed energy deposition (L-DED) process, and particularly to a coaxial tungsten electrode conductive magnetoelectric coupling laser powder deposition device and method. Background Technology

[0002] Laser-driven directed energy deposition (L-DED) uses a laser as a heat source and a carrier gas to carry metal powder into the laser-acting zone to form a molten pool and deposit it layer by layer. It has the advantages of high deposition efficiency, flexible trajectory, and suitability for manufacturing and repairing complex curved surfaces and large components. It has important application prospects in the field of manufacturing and repairing high-temperature alloy parts for aero-engines. However, the molten pool size in L-DED is usually on the millimeter or even sub-millimeter scale. The temperature gradient is large and the cooling rate is high. Intense Marangoni convection, backflow vortex and non-equilibrium solidification are easily generated inside the molten pool, which leads to the following typical problems: (1) When depositing single-crystal high-temperature alloys, strong convection inside the molten pool can easily destroy the directional solidification conditions and induce the nucleation of impurity crystals, causing the single crystal continuity to be destroyed; (2) When depositing polycrystalline high-temperature alloys, columnar dendrites are easy to coarsen and penetrate between layers, superimposed thermal stress concentration, which can easily lead to hot cracks; (3) Rapid flow of the molten pool can cause forming quality defects, such as uneven surface, element segregation and porosity inclusions.

[0003] Existing technologies attempt to use external magnetic or electric fields to interfere with the flow and solidification of the molten pool, but there are still significant shortcomings:

[0004] The scheme that relies solely on an external magnetic field depends on the weak current (milliampere level) generated by the thermoelectric effect within the molten pool. A strong magnetic field (>1T) is required to obtain sufficient Lorentz force, resulting in a large magnetic field device that requires water cooling, is difficult to integrate with the deposition head, and may affect powder trajectory and deposition stability.

[0005] Fixed clamping electrode current diversion schemes (such as introducing applied current through lateral clamps or substrate electrodes) have the problem that the current path is unstable due to dynamic changes in the position of the molten pool, the resistance of the molten pool and the contact state. It is difficult to form a stable and repeatable volume force distribution inside the molten pool, and the spatial coordination with the deposition head is poor.

[0006] In existing magnetic field and electric field composite schemes, the magnetic field is mostly fixed, and the current introduction method is limited to indirect coupling far away from the molten pool. It lacks coaxial alignment and follow-up holding capability with the laser molten pool, which makes it impossible to accurately control and stably reproduce the current flow path and the spatial distribution of the Lorentz force field in the molten pool.

[0007] Existing solutions lack multiple switchable in-situ "magnetic-electric" control modes for the L-DED process. It is impossible to switch between "braking mode to suppress convection" and "oscillation mode to promote stirring" on the same equipment by switching the current waveform, making it difficult to simultaneously cover the two typical needs of single crystal / directional columnar epitaxial growth and polycrystalline refinement.

[0008] Therefore, there is an urgent need for a technical solution that can actively establish a strong, controllable and switchable Lorentz force field inside the laser powder feeding molten pool, while being able to be integrated with the powder feeding deposition head in a lightweight and dynamic manner without interfering with powder feeding and protective gas. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the prior art and provide a coaxial tungsten electrode conductive magnetoelectric coupling laser powder delivery deposition device and method. This device can actively construct a strong, controllable and switchable Lorentz force field inside the laser powder delivery directional energy deposition molten pool, so as to achieve fine control of the molten pool flow, heat transfer and solidification behavior at the millimeter scale. This improves the epitaxial growth quality of the single crystal / directional solidification alloy deposition process, or refines polycrystalline grains, and suppresses solidification cracking caused by element segregation and thermal stress concentration, while ensuring engineering compatibility with laser powder delivery technology.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: In a first aspect, the present invention provides a coaxial tungsten electrode conductive magnetoelectric coupling laser powder deposition device, comprising: A laser powder feeding deposition module includes a laser and a laser powder feeding deposition head. The laser powder feeding deposition head is configured to output a multi-beam laser array and cooperates with an outer powder feeding channel to allow metal powder to converge in the laser action area under the action of a carrier gas, forming a molten pool on the substrate surface or the deposited layer. The coaxial current injection assembly includes a tungsten needle electrode disposed on the central axis of the laser powder deposition head, and a programmable power supply electrically connecting the tungsten needle electrode to the substrate; the axis of the tungsten needle electrode coincides with the integrated axis of the multi-beam laser array, and the end of the tungsten needle electrode is located 1-2 mm above the surface of the molten pool, forming a micro-beam plasma arc, which acts as a conductive channel to inject applied current into the molten pool; the programmable power supply can switch between DC and AC output modes. A transverse magnetic field generating unit is integrated into the laser powder feeding deposition head and moves synchronously with it. It is used to generate a transverse magnetic field in the molten pool region. The magnetic induction lines of the transverse magnetic field are perpendicular to the deposition scanning path and parallel to the substrate surface. The powder feeding and gas management component is used to provide metal powder, carrier gas and protective gas to the laser powder feeding deposition head, and to maintain the stability of powder beam convergence and microbeam plasma arc. 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 from the tungsten needle electrode, micro-beam plasma arc, molten pool region, substrate to the reflow fixture. The control unit is connected to the laser, the laser powder delivery and deposition head, the programmable power supply and the transverse magnetic field generating unit respectively, and is used to coordinate the adjustment of laser power, powder delivery rate, deposition scanning rate, current parameters and transverse magnetic field parameters. The applied current and the transverse magnetic field interact within the molten pool to generate Lorentz force, thereby actively regulating the flow, heat transfer, and solidification behavior within the molten pool and achieving controllable adjustment of the microstructure and defects.

[0011] Preferably, the laser powder delivery head is a multi-laser beam integrated powder delivery head, and the powder delivery method is annular cavity powder delivery or annular array multi-beam powder delivery. The powder is carried by a carrier gas and converged to the central region of the molten pool through the annular cavity or multi-beam channel. The carrier gas is argon, helium or other protective gas. The tungsten needle electrode is set in the hollow structure at the center of the powder beam convergence, so that the tungsten needle electrode does not block the powder beam and is coaxially aligned with the molten pool.

[0012] Furthermore, the tungsten needle electrode is a cerium-tungsten or lanthanum-tungsten electrode with a diameter of 0.5~1.0 mm, and the tip has a micro-blunt conical structure with a cone angle of 20°~30° and retains a platform with a diameter of 0.1~0.2 mm; the current range introduced into the molten pool by the micro-beam plasma arc is 20~50A, and the arc column diameter is 0.8~1.5 mm. The tungsten needle electrode is cooled by a protective gas to suppress electrode heat loss and extend electrode life.

[0013] Furthermore, the transverse magnetic field generating unit is an electromagnetic coil assembly, which generates a transverse magnetic field strength of 0.05~0.1T. The magnetic field direction is switched by reversing the positive and negative poles of the electromagnetic coil assembly, and the magnetic field strength is adjusted by regulating the excitation current of the electromagnetic coil assembly. The transverse magnetic field generating unit is fixedly connected to the laser powder delivery deposition head through an integrated mounting bracket, so that the magnetic field maintains a relatively fixed spatial relationship with the molten pool and acts synchronously on the molten pool as the laser powder delivery deposition head moves.

[0014] Furthermore, the programmable power supply outputs a directional current from the tungsten needle electrode to the substrate in DC mode, generating a directional Lorentz braking force field under the action of a transverse magnetic field; in AC mode, it outputs an alternating current with a frequency of 50~100Hz, generating a periodically changing Lorentz oscillating force field under the action of a transverse magnetic field.

[0015] Furthermore, the powder feeding and gas management component includes a carrier gas channel, an inner protective gas channel, an outer protective gas channel, and a micro-beam plasma arc auxiliary gas channel; the carrier gas in the carrier gas channel is used to transport and concentrate the metal powder, the inner protective gas in the inner protective gas channel is used to protect the optical system, the outer protective gas in the outer protective gas channel is used to isolate air, and the auxiliary gas in the auxiliary gas channel is used to stabilize the micro-beam plasma arc morphology.

[0016] Furthermore, the tungsten needle electrode achieves extension length adjustment through an electrode position adjustment mechanism to automatically compensate for wear and maintain the distance between the tungsten needle and the workpiece without contacting the high-temperature molten pool, ensuring the stability of the conductive path of the micro-beam plasma arc; the electrode position adjustment mechanism is any one or a combination of a fine-tuning threaded pair, a linear slide, or a motor screw mechanism; this adjustment is independent of the working distance adjustment between the laser powder feeding deposition head and the substrate, achieving decoupled control.

[0017] Furthermore, the control unit programs and controls the parameters of the applied current, including the amplitude and polarity of the DC current, the effective value, frequency and waveform characteristics of the AC current, and coordinates the control of the laser power and spot diameter, the shape of the micro-beam plasma arc, the powder feeding rate and gas flow rate, as well as the direction of the magnetic induction lines, the magnetic induction intensity and on / off state of the magnetic field generating unit, thereby dynamically adjusting the intensity and mode of the Lorentz force field in the molten pool during the deposition process.

[0018] Secondly, the present invention provides a coaxial tungsten electrode conductive magnetoelectric coupling laser powder deposition method, implemented using the above-mentioned device, comprising the following steps: The transverse magnetic field generating unit is activated to generate a transverse magnetic field in the area to be deposited. The direction of the magnetic induction lines of the transverse magnetic field is perpendicular to the direction of the deposition scanning path and parallel to the substrate surface. The powder feeding and gas management components are activated to supply metal powder, carrier gas and protective gas to the laser powder deposition head, so that the powder beam can be stably converged in the laser action area. The laser is activated to form a molten pool in the area of ​​the substrate to be processed, and at the same time, the tungsten needle electrode is excited to establish a micro-beam plasma arc conductive channel that penetrates the molten pool. The applied current mode is selected based on the alloy material to be processed and the microstructure target: when the material is a single crystal or a directionally solidified alloy, the DC mode is selected; when the material is polycrystalline or requires grain refinement, the AC mode is selected; and the matching of the current parameters and magnetic field parameters is adjusted through the control unit. During the deposition scanning process, the applied current and the transverse magnetic field are coupled in the molten pool to generate a Lorentz force field, which actively regulates the flow, heat transfer and solidification of the molten pool; after deposition, the current is cut off and the magnetic field is turned off or the magnetic field is maintained until the molten pool solidification is completed.

[0019] Furthermore, in the DC mode, the applied DC current flows from the tungsten needle electrode to the substrate through the micro-beam plasma arc, and couples with the transverse magnetic field to generate a stable Lorentz braking force field. Through the Hartmann effect, electromagnetic damping is generated on the molten pool flow field, suppressing Marangoni convection, maintaining a stable temperature gradient and solidification interface morphology, thereby avoiding heterogeneous grain nucleation and realizing the growth of single crystals or directionally solidified alloys without impurities.

[0020] Furthermore, in the AC mode, the applied AC current periodically alternates, coupling with the transverse magnetic field to generate an alternating Lorentz oscillation force, inducing forced oscillation of the molten pool, causing the liquid metal in the molten pool to form a periodic shear flow, breaking up the primary dendrites and promoting the transformation of columnar crystals to equiaxed crystals, refining the solidification structure and reducing the sensitivity to hot cracking, thereby achieving grain refinement and crack suppression in the polycrystalline alloy deposition process.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects: High electromagnetic coupling efficiency: The coaxial structure used in this invention ensures that the laser heating area and the current injection path are completely aligned. The micro-beam plasma arc has good stiffness and directional stability, and is not easily disturbed by the protective gas flow or molten pool convection, ensuring that the current can be continuously and stably injected into the molten pool, greatly improving the controllability and efficiency of the electromagnetic force on the molten pool.

[0022] Lightweight and dynamically integrated device: This invention eliminates the reliance on ultra-strong static magnetic fields, achieving significant results with a moderately strong magnetic field (0.05T~0.1T) combined with an applied current. This allows for the miniaturization and lightweighting of the magnetic field generator, enabling it to be directly mounted on the deposition head and operated dynamically without the need for a bulky fixed magnetic field mechanism and cooling device. This is beneficial for the manufacturing and repair of complex trajectories and large-scale components.

[0023] Improved quality of single-crystal epitaxy: In the electromagnetic braking mode of DC electric current + magnetic field, the Lorentz force in the molten pool produces a "damping" effect on the flow, which can effectively suppress Marangoni convection in the molten pool, fundamentally eliminate the convective transport conditions required for the nucleation of impurity crystals, make the temperature gradient at the solidification front of the molten pool more stable, and ensure the integrity rate of single crystals with consistent orientation between the deposited layer and the matrix.

[0024] Polycrystalline structure refinement and defect suppression: In this invention, under the electromagnetic oscillation mode of alternating current and magnetic field, the molten pool is disturbed by periodic Lorentz forces, and the liquid metal forms oscillating eddies. This applies repeated shear stress to the growing columnar dendrites, causing them to fracture and promoting the formation of new crystal nuclei, thereby facilitating the transformation of columnar crystals into equiaxed crystals and refining the grain size. Simultaneously, due to the fine and uniform grain size, thermal stress is homogenized and released, significantly reducing the hot cracking sensitivity of polycrystalline alloy deposition and improving the forming quality.

[0025] Multi-functionality and mode switching: This invention allows the same device to switch between "electromagnetic braking" and "electromagnetic oscillation" modes simply by changing the power output mode. This enables the selection of the optimal control strategy based on the needs of different alloy materials and process stages. For example, when repairing single-crystal blades, DC mode is used to ensure directional epitaxial growth of the single crystal; when manufacturing polycrystalline structural components, AC mode is switched to promote the formation of equiaxed crystals. This multi-functionality expands the application range of the equipment and improves its process adaptability.

[0026] The present invention provides a coaxial tungsten electrode conductive magnetoelectric coupling laser powder deposition device and method, which can autonomously control the crystal texture by changing the flow and solidification behavior of the molten pool without significantly increasing the complexity of the system, thereby improving the microstructure quality and performance of high-value metal components for deposition manufacturing or repair and meeting the needs of industrial applications. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of the coaxial tungsten electrode conductive magnetoelectric coupling laser powder delivery deposition device according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the current path and transverse magnetic field distribution within the molten pool in an embodiment of the present invention; Figure 3 The diagrams show a comparison of the solidification interface in the molten pool under non-electromagnetic braking and DC electromagnetic braking modes, where (a) is a schematic diagram without electromagnetic braking and (b) is a schematic diagram under DC electromagnetic braking mode. Figure 4 This is a schematic diagram illustrating the effect of Lorentz braking force in the molten pool under DC electromagnetic braking mode in an embodiment of the present invention. Figure 5 This is a schematic diagram of the dendrite breakage and grain refinement principle under AC electromagnetic oscillation mode in an embodiment of the present invention, wherein (a) is the periodic variation curve of Lorentz force under AC current, and (b) is a schematic diagram of the molten pool oscillation and grain refinement principle. Figure 6 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.

[0028] Explanation of reference numerals in the attached figures: 1-Laser; 2-Laser powder delivery head; 3-Multi-beam laser array; 4-Contact contact nozzle; 5-Electrode position adjustment mechanism; 6-Programmable power supply; 7-Micro-beam plasma arc; 8-Transverse magnetic field generating unit; 9-Electromagnetic coil; 10-Mounting bracket; 11-Carrier gas powder delivery channel; 12-Protective gas channel; 13-Auxiliary gas channel; 14-Gas curtain ring; 15-Sensing feedback system; 16-Control unit; 17-Substrate; 18-Molten pool; 19-Powder beam; 20-Tungsten needle electrode; 21-Scanning direction; 22-Reflow fixture. Detailed Implementation

[0029] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0030] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application 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 this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] like Figure 1 As shown, the coaxial tungsten electrode conductive magnetoelectric coupling laser powder deposition device provided in this embodiment of the invention includes: The laser powder deposition module includes a laser 1 and a laser powder deposition head 2, which are connected by an optical fiber. The laser powder deposition head 2 is configured to output a multi-beam laser array 3 (e.g., four or six laser beams symmetrically distributed in a ring), which is focused on the surface of the substrate 17 to form a molten pool 18. The laser powder deposition head 2 is a multi-laser integrated powder deposition head, and the powder delivery method is either ring cavity powder delivery or ring array multi-beam powder delivery. The powder is carried by a carrier gas, such as argon, helium, or other protective gas, and converges to the central region of the molten pool through the ring cavity or multi-beam channels.

[0032] The coaxial current injection assembly includes a tungsten needle electrode 20 disposed inside the laser powder deposition head 2 and arranged coaxially with its central axis, and a programmable power supply 6 electrically connecting the tungsten needle electrode 20 to the substrate 17. The axis of the tungsten needle electrode 20 coincides with the integrated axis of the multi-beam laser array 3. The upper end of the tungsten needle electrode 20 is electrically connected to the positive electrode of the programmable power supply 6 through a contact conductive nozzle 4, and the lower end extends close to the surface of the molten pool 18, with the lower end located 1-2 mm above the surface of the molten pool 18. An auxiliary gas (such as argon) is provided through the auxiliary gas channel 13 and excited by the programmable power supply 6 to form a micro-beam plasma arc 7. The tungsten needle electrode 20 is disposed in a hollow structure at the center of the powder beam convergence, so that the tungsten needle electrode 20 does not obstruct the powder beam and is coaxially aligned with the molten pool.

[0033] The return terminal of the programmable power supply 6 is electrically connected to the substrate 17 or the tooling fixture through the return fixture 22, forming a closed current loop through the tungsten needle electrode, the micro-beam plasma arc, the molten pool region, the substrate and the return fixture.

[0034] A transverse magnetic field generating unit 8 is fixedly mounted on the outer periphery of the laser powder feeding deposition head 2 via a mounting bracket 10. The transverse magnetic field generating unit 8 includes an electromagnetic coil 9 for generating a transverse magnetic field in the molten pool region 18. The transverse magnetic field generating unit 8 is fixedly connected to the laser powder feeding deposition head 2 and moves synchronously with the laser powder feeding deposition head 2, thereby ensuring that the magnetic field always covers the molten pool region and its direction remains constant relative to the scanning path during the deposition process.

[0035] The electrode position adjustment mechanism 5 is connected to the tungsten needle electrode 20 and is used to precisely adjust the extension length of the end of the tungsten needle electrode 20 relative to the surface of the molten pool 18. The electrode position adjustment mechanism 5 is any one or a combination of a fine-tuning threaded pair, a linear slide, or a motor screw mechanism.

[0036] The powder feeding and gas management assembly includes a carrier gas powder feeding channel 11, a protective gas channel 12, an auxiliary gas channel 13, and a gas curtain ring 14. The carrier gas powder feeding channel 11 delivers metal powder and a carrier gas (such as argon) to the laser powder deposition head 2. The powder beam 19 is ejected from a nozzle below the laser powder deposition head 2 and converges in the central region of the molten pool 18. The protective gas channel 12 includes an inner protective gas channel and an outer protective gas channel, outputting inner and outer protective gases (such as argon) respectively. The inner protective gas in the inner protective gas channel protects the optical system, while the outer protective gas in the outer protective gas channel forms a gas curtain around the molten pool 18 to isolate air. The auxiliary gas channel 13 supplies auxiliary gas (such as argon) to the vicinity of the tungsten needle electrode 20 to stabilize the morphology of the micro-beam plasma arc 7. The gas curtain ring 14 is positioned around the tungsten needle electrode 20 to reduce the disturbance of the arc column caused by powder backflow and to prevent powder adhesion from causing short circuits.

[0037] The control unit 16 is electrically connected to the laser 1, the laser powder delivery and deposition head 2, the programmable power supply 6, the electrode position adjustment mechanism 5, the transverse magnetic field generating unit 8, the powder delivery and gas management components, and the sensor feedback system 15. It is used to coordinate the control of laser power and spot diameter, powder delivery rate and gas flow rate, the current waveform (morphology) of the micro-beam plasma arc, and the intensity, direction, and on / off state of the transverse magnetic field, thereby dynamically adjusting the intensity and mode of the Lorentz force field within the molten pool during the deposition process. The sensor feedback system 15 connects the electrode position adjustment mechanism 5, the laser powder delivery and deposition head 2, and the control unit 16. The control unit 16 can programmably set current parameters (amplitude and polarity of DC, effective value, frequency, and waveform characteristics of AC) and magnetic field strength. It can also be combined with the sensor feedback system 15 (such as an infrared thermometer, a high-speed camera, or an electrical parameter sensor) to monitor molten pool temperature, morphology, magnetic field, and other parameters in real time, achieving closed-loop regulation.

[0038] like Figure 2As shown, when the laser powder deposition head 2 starts working, the multi-beam laser array 3 forms a molten pool 18 on the surface of the substrate 17. Simultaneously, the programmable power supply 6 supplies power to the tungsten needle electrode 20, exciting a micro-beam plasma arc 7 between the end of the tungsten needle electrode 20 and the surface of the molten pool 18. The diameter of the arc column of this micro-beam plasma arc 7 is preferably 0.8~1.5 mm, and the current introduced into the molten pool by the micro-beam plasma arc is in the range of 20~50 A. The micro-beam plasma arc 7 acts as a flexible conductive channel, stably injecting the applied current from the tungsten needle electrode 20 into the interior of the molten pool 18, and then returning it to the programmable power supply 6 via the substrate 17 and the return clamp 22, forming a closed loop. Since the resistance of the liquid molten pool 18 is much smaller than that of the solid substrate, the applied current is mainly concentrated in the molten pool region. To avoid the thermal input of the micro-beam plasma arc altering the energy dominance mechanism of the deposited molten pool, the micro-beam plasma arc 7 is limited to a weak arc channel.

[0039] The tungsten needle electrode 20 is preferably made of cerium-tungsten (WC20) or lanthanum-tungsten (WL20) electrode material with a diameter of 0.5~1.0 mm. Its tip is machined into a micro-blunt conical structure with a cone angle of 20°~30°, and retains a small platform with a diameter of about 0.1~0.2 mm to facilitate the stable initiation and maintenance of the micro-beam plasma arc 7. The distance between the end of the tungsten needle electrode 20 and the surface of the molten pool 18 is controlled at 1~2 mm. This distance is precisely adjusted by the electrode position adjustment mechanism 5. This adjustment is independent of the working distance adjustment between the laser powder feeding deposition head 2 and the substrate 17, which can achieve decoupled control and ensure that when the tungsten needle electrode 20 shortens due to wear during long-term deposition, it can be compensated in time to maintain a stable arc length.

[0040] In this embodiment of the invention, the transverse magnetic field generating unit 8 is an electromagnetic coil assembly. The electromagnetic coil 9 within the assembly is supplied with a DC excitation current, generating a time-constant transverse magnetic field in the molten pool 18 region. The magnetic induction lines of this magnetic field are perpendicular to the deposition scanning direction 21 and parallel to the surface of the substrate 17 (e.g., ...). Figure 2 As shown, the magnetic field direction is perpendicular to the paper or along the horizontal direction. The horizontal magnetic field strength ranges from 0.05 to 0.1 T. The magnetic field strength can be continuously adjusted by adjusting the excitation current of the electromagnetic coil assembly, and the magnetic field direction can be switched by reversing the positive and negative poles of the electromagnetic coil assembly.

[0041] Since the transverse magnetic field generating unit 8 is fixedly connected to the laser powder delivery deposition head 2 and moves synchronously with it, the relative spatial relationship between the magnetic field and the molten pool 18 remains constant during the deposition scanning process, ensuring the consistency of the Lorentz force direction.

[0042] This invention provides two working modes: Electromagnetic braking mode (DC + transverse magnetic field): such as Figure 3 and Figure 4As shown, when the programmable power supply 6 outputs a DC current I (e.g., 20~50A), the applied current flows vertically downwards from the tungsten needle electrode 20 through the micro-beam plasma arc 7 to the molten pool 18 and the substrate 17. This DC current I interacts with the transverse magnetic field (direction perpendicular to the scanning direction), generating a constant-direction Lorentz braking force F inside the molten pool 18 according to the left-hand rule. L This braking force provides electromagnetic damping (Hartmann effect) to the Marangoni convection driven by the surface tension gradient within the molten pool, suppressing disordered flow and eddies, and making the temperature gradient and solidification interface within the molten pool 18 more stable (e.g., Figure 3 As shown in (b) of the diagram, the solidification interface tends to be flat. This mode is suitable for the deposition or repair of single-crystal or directionally solidified alloys, effectively avoiding impurity crystal nucleation and promoting epitaxial growth. Figure 3 As shown in (a), in the non-electromagnetic braking mode, intense Marangoni convection was generated, and heterogeneous crystal nucleation occurred.

[0043] Electromagnetic oscillation mode (AC + transverse magnetic field): such as Figure 5 and Figure 6 As shown, when the programmable power supply 6 outputs AC current I AC (When the output effective value of the alternating current is 20~50A and the frequency is 50~100Hz in this AC mode, the direction of the applied current alternates periodically with time. Under the action of the transverse magnetic field, the oscillating Lorentz force F generated in the molten pool 18 L It also changes periodically, such as Figure 5 As shown in (a) above. This alternating Lorentz force drives the molten metal in the pool to produce forced oscillations and periodic shear flows (such as...). Figure 6 (As indicated by the arrow inside the molten pool). Figure 5 As shown in (b), this oscillatory shearing action can effectively break up growing primary dendrites, interrupt dendrite arms, and promote the formation of new crystal nuclei (such as equiaxed crystal nuclei, fine equiaxed crystals, and equiaxed nuclei in the figure), thereby promoting the transformation of columnar crystals into equiaxed crystals and refining the solidification structure. Simultaneously, the stirring of the molten pool facilitates the upward escape of bubbles and inclusions, resulting in a uniform solute distribution and reduced susceptibility to hot cracking. This mode is suitable for the deposition of polycrystalline alloys.

[0044] This invention also provides a coaxial tungsten electrode conductive magnetoelectric coupling laser powder deposition method, implemented using the above-mentioned apparatus, comprising the following steps: The transverse magnetic field generating unit 8 is activated to generate a transverse magnetic field in the area to be deposited. The direction of the magnetic induction lines of the transverse magnetic field is perpendicular to the direction of the deposition scanning path and parallel to the surface of the substrate 17. The powder feeding and gas management components are activated to supply metal powder, carrier gas and protective gas to the laser powder feeding deposition head 2, so that the powder beam can be stably converged in the laser action area. Laser 1 is activated to form a molten pool 18 in the area to be processed on substrate 17, while coaxial tungsten needle electrode 20 is excited to establish a micro-beam plasma arc conductive channel that penetrates the molten pool 18. Select the applied current mode according to the alloy material to be processed and the microstructure target: when the material is a single crystal or a directionally solidified alloy, select the DC mode; when the material is polycrystalline or requires grain refinement, select the AC mode. During the deposition scanning process, the applied current and the transverse magnetic field are coupled in the molten pool 18 to generate a Lorentz force field, which actively regulates the flow, heat transfer and solidification of the molten pool; after the deposition is completed, the current is cut off and the magnetic field is turned off or the magnetic field is maintained until the molten pool solidification is completed.

[0045] In the DC mode, the applied DC current flows from the tungsten needle electrode 20 through the micro-beam plasma arc 7 to the substrate 17, and couples with the transverse magnetic field to generate a stable Lorentz braking force field. Through the Hartmann effect, electromagnetic damping is generated on the molten pool flow field, suppressing Marangoni convection, maintaining a stable temperature gradient and solidification interface morphology, and realizing the growth of single crystal or directionally solidified alloy without impurities.

[0046] In alternating current mode, the applied alternating current periodically alternates and couples with the transverse magnetic field to generate alternating Lorentz oscillation force, which induces forced oscillation of the molten pool, causing the liquid metal in the molten pool to form periodic shear flow, breaking up primary dendrites and promoting the transformation of columnar crystals into equiaxed crystals, thereby achieving grain refinement and crack suppression in the polycrystalline alloy deposition process.

[0047] The following are specific embodiments of the coaxial tungsten electrode conductive magnetoelectric coupling laser powder deposition device and method described in this invention.

[0048] Example 1: Repair of René N5 monocrystalline blades (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. Before deposition, the area to be repaired was polished, degreased, and dried, and the deposition scanning direction was aligned with the primary dendrite orientation of the matrix or the predetermined epitaxial growth direction. Figure 1 The apparatus shown is used for repair deposition. The laser power is 800~1600 W (preferably 1200 W); the laser spot diameter is 1.0~2.0 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); an outer protective gas flow rate of 8~15 L / min (preferably 10 L / min); and a micro-beam plasma arc auxiliary gas flow rate of 1~3 L / min (preferably 2 L / min).

[0049] In this embodiment, the tungsten needle electrode 20 is a cerium-tungsten electrode with a diameter of 0.8 mm, and its end is about 1.5 mm away from the molten pool. The micro-beam plasma arc current is 20~50 A (preferably 40~50 A). The transverse magnetic field strength is 0.05~0.1 T (preferably 0.05~0.08 T), and its direction is perpendicular to the scanning direction. Deposition is performed using a DC electromagnetic braking mode.

[0050] During deposition, the applied DC current couples with the steady-state transverse magnetic field, forming a stable Lorentz braking field within the molten pool 18. This braking field electromagnetically dampens the Marangoni convection and backflow eddies generated along the surface tension gradient within the molten pool, reducing surface fluctuations and stabilizing the solid-liquid interface morphology. Simultaneously, the introduction of weakly pulsating current facilitates the upward escape of inclusions in the molten pool, reducing or essentially eliminating porosity in the deposited layer. The results show that the repaired area maintains continuous epitaxial growth with the single-crystal matrix, impurities and low-angle grain boundaries are significantly reduced, and the solidification structure on the surface of the deposited layer is more straight and continuous.

[0051] Example 2: Deposition of IN718 polycrystalline superalloy (electromagnetic oscillation mode) In this embodiment, IN718 alloy powder is used for multi-channel, multi-layer laser-fed directional energy deposition on a nickel-based alloy substrate. The powder particle size is 53-150 μm. The laser powder deposition head 2 is a coaxial multi-channel powder feeding structure. A gas curtain ring 14 is set around the tungsten needle electrode 20 to enhance the resistance to powder intrusion and stabilize the arc column. The laser power is 1000-1800 W (preferably 1400 W); the laser spot diameter is 1.0-2.0 mm (preferably 1.5 mm); the powder feeding rate is 6-14 g / min (preferably 8 g / min); 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); argon is used as the outer protective gas, with a flow rate of 10-20 L / min (preferably 15 L / min); and the flow rate of the micro-beam plasma arc auxiliary gas is 1-4 L / min (preferably 2.5 L / min). The transverse magnetic field strength is 0.05~0.1T (preferably 0.05~0.08T), and its direction is perpendicular to the scanning direction. An AC electromagnetic oscillation mode is used, with an effective AC current of 20~50 A (preferably 40~50 A) and a frequency of 50~100 Hz.

[0052] During deposition, the AC applied current couples with the transverse magnetic field to form a periodically alternating Lorentz oscillation force, placing the molten pool 18 in an electromagnetic oscillation mode. This mode induces forced vibration and periodic shearing in the liquid metal, breaking up growing columnar dendrites and promoting equiaxed crystal nucleation, thereby refining the grain size of the polycrystalline deposition layer. Simultaneously, molten pool stirring homogenizes the temperature field and solute distribution, reduces elemental segregation and thermal stress concentration, inhibits the formation of solidification cracks and interlayer cracks, and facilitates bubble migration and escape, reducing porosity defects in the deposition layer. The post-deposition microstructure shows that the columnar crystals are broken up, the proportion of equiaxed crystals is significantly increased, the grain size is 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, a nickel-based high-temperature alloy wire (such as IN718) is selected for laser wire-feed directional energy deposition. The wire diameter is 0.8~1.2 mm, preferably 1.0 mm. The laser power is 800~2500 W, preferably 1200 W; 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 powder deposition head 2. The wire feeding channel can be located off-center from the central axis, with its outlet extending above the molten pool 18 or to the leading edge region of the molten pool 18. The metal wire is continuously fed into the molten pool 18 via the wire feeding mechanism and the wire feeding channel. The tungsten needle electrode 20 is still located on the central axis of the deposition head, and a clearance space is maintained between the wire feeding path and the tungsten needle electrode 20, so that the tungsten needle electrode 20 does not block the wire feeding path, and the wire does not interfere with the conductive channel of the micro-beam plasma arc 7 between the tungsten needle electrode 20 and the molten pool 18.

[0055] During deposition, the applied current is still supplied by the programmable power supply 6 through the contact conductive nozzle 4 to the tungsten needle electrode 20, and injected into the molten pool 18 through the micro-beam plasma arc 7. Coupled with the transverse magnetic field, it generates a Lorentz force to regulate the flow, heat transfer, and solidification behavior of the molten pool. Depending on the material type and microstructure target, either the electromagnetic braking mode (DC) or the electromagnetic oscillation mode (AC) can be selected. The filament and powder can be used alone 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 coaxial tungsten electrode conductive magnetoelectric coupling laser powder deposition device, characterized in that, include: A laser powder feeding deposition module includes a laser and a laser powder feeding deposition head. The laser powder feeding deposition head is configured to output a multi-beam laser array and cooperates with an outer powder feeding channel to allow metal powder to converge in the laser action area under the action of a carrier gas, forming a molten pool on the substrate surface or the deposited layer. The coaxial current injection assembly includes a tungsten needle electrode disposed on the central axis of the laser powder deposition head, and a programmable power supply electrically connecting the tungsten needle electrode to the substrate; the axis of the tungsten needle electrode coincides with the integrated axis of the multi-beam laser array, and the end of the tungsten needle electrode is located 1-2 mm above the surface of the molten pool, forming a micro-beam plasma arc, which acts as a conductive channel to inject applied current into the molten pool; the programmable power supply can switch between DC and AC output modes. A transverse magnetic field generating unit is integrated into the laser powder feeding deposition head and moves synchronously with it. It is used to generate a transverse magnetic field in the molten pool region. The magnetic induction lines of the transverse magnetic field are perpendicular to the deposition scanning path and parallel to the substrate surface. The powder feeding and gas management component is used to provide metal powder, carrier gas and protective gas to the laser powder feeding deposition head, and to maintain the stability of powder beam convergence and microbeam plasma arc. 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 from the tungsten needle electrode, micro-beam plasma arc, molten pool region, substrate to the reflow fixture. The control unit is connected to the laser, the laser powder delivery and deposition head, the programmable power supply and the transverse magnetic field generating unit respectively, and is used to coordinate the adjustment of laser power, powder delivery rate, deposition scanning rate, current parameters and transverse magnetic field parameters. The applied current and the transverse magnetic field interact within the molten pool to generate Lorentz force, thereby actively regulating the flow, heat transfer, and solidification behavior within the molten pool.

2. The apparatus according to claim 1, characterized in that: The tungsten needle electrode is a cerium-tungsten or lanthanum-tungsten electrode with a diameter of 0.5~1.0 mm, and the tip is a micro-blunt conical structure with a cone angle of 20°~30° and retains a platform with a diameter of 0.1~0.2 mm; the current range introduced into the molten pool by the micro-beam plasma arc is 20~50A, and the arc column diameter is 0.8~1.5 mm.

3. The apparatus according to claim 1, characterized in that: The transverse magnetic field generating unit is an electromagnetic coil assembly, which generates a transverse magnetic field strength of 0.05~0.1T. The magnetic field direction is switched by reversing the positive and negative poles of the electromagnetic coil assembly, and the magnetic field strength is adjusted by adjusting the excitation current of the electromagnetic coil assembly.

4. The apparatus according to claim 1, characterized in that: The programmable power supply outputs a directional current from the tungsten needle electrode to the substrate in DC mode, generating a directional Lorentz braking force field under the action of a transverse magnetic field; in AC mode, it outputs an alternating current with a frequency of 50~100Hz, generating a periodically changing Lorentz oscillating force field under the action of a transverse magnetic field.

5. The apparatus according to claim 1, characterized in that: The powder feeding and gas management component includes a carrier gas channel, an inner protective gas channel, an outer protective gas channel, and a micro-beam plasma arc auxiliary gas channel. The carrier gas in the carrier gas channel is used to transport and concentrate the metal powder. The inner protective gas in the inner protective gas channel is used to protect the optical system. The outer protective gas in the outer protective gas channel is used to isolate air. The auxiliary gas in the auxiliary gas channel is used to stabilize the shape of the micro-beam plasma arc.

6. The apparatus according to claim 1, characterized in that: The extension length of the tungsten needle electrode is adjusted by an electrode position adjustment mechanism, which is any one or a combination of a fine-tuning threaded pair, a linear slide, or a motor screw mechanism; this adjustment is independent of the working distance adjustment between the laser powder feeding deposition head and the substrate.

7. The apparatus according to claim 1, characterized in that: The control unit programs and controls the parameters of the applied current, including the amplitude and polarity of the DC current, the effective value, frequency and waveform characteristics of the AC current, and coordinates the control of the laser power, powder feeding rate, deposition scanning rate, gas flow rate, and the magnetic induction intensity and on / off state of the magnetic field generating unit.

8. A coaxial tungsten electrode conductive magnetoelectric coupling laser powder deposition method, implemented using the apparatus described in any one of claims 1 to 7, characterized in that, Includes the following steps: The transverse magnetic field generating unit is activated to generate a transverse magnetic field in the area to be deposited. The direction of the magnetic induction lines of the transverse magnetic field is perpendicular to the direction of the deposition scanning path and parallel to the substrate surface. The powder feeding and gas management components are activated to supply metal powder, carrier gas and protective gas to the laser powder deposition head, so that the powder beam can be stably converged in the laser action area. The laser is activated to form a molten pool in the area of ​​the substrate to be processed, and at the same time, the tungsten needle electrode is excited to establish a micro-beam plasma arc conductive channel that penetrates the molten pool. Select the applied current mode according to the alloy material to be processed and the microstructure target: when the material is a single crystal or a directionally solidified alloy, select the DC mode; when the material is polycrystalline or requires grain refinement, select the AC mode. During the deposition scanning process, the applied current and the transverse magnetic field are coupled in the molten pool to generate a Lorentz force field, which actively regulates the flow, heat transfer and solidification of the molten pool. After deposition is complete, the current is cut off and the magnetic field is turned off, or the magnetic field is maintained until the molten pool solidifies.

9. The method according to claim 8, characterized in that: In the DC mode, the applied DC current flows from the tungsten needle electrode to the substrate through the micro-beam plasma arc, and couples with the transverse magnetic field to generate a stable Lorentz braking force field. Through the Hartmann effect, electromagnetic damping is generated on the molten pool flow field, suppressing Marangoni convection, maintaining a stable temperature gradient and solidification interface morphology, and realizing the growth of single crystal or directionally solidified alloys without impurities.

10. The method according to claim 8, characterized in that: In the alternating current mode, the applied alternating current periodically alternates and couples with the transverse magnetic field to generate alternating Lorentz oscillation force, which induces forced oscillation of the molten pool, causing the liquid metal in the molten pool to form periodic shear flow, breaking up primary dendrites and promoting the transformation of columnar crystals into equiaxed crystals, thereby achieving grain refinement and crack suppression in the polycrystalline alloy deposition process.

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