A method and system for regulating a laser cladding process with the assistance of an energy field

Abstract

This invention relates to the fields of laser additive manufacturing and surface engineering, and particularly to a method and system for controlling laser cladding processes assisted by an energy field. This invention simultaneously introduces a first melt flow induced by the periodic spatial motion of a laser and a second melt flow generated by an alternating magnetic field into a conductive molten pool. By adjusting the vector direction, frequency, and phase relationship between the two flows, they are switched between synergistic states such as enhanced stirring, periodic shearing, or flow suppression, thereby altering the synthetic flow structure within the molten pool and achieving active control over molten pool stability, gas expulsion, and grain growth behavior. Furthermore, the synergistic state is dynamically adjusted based on real-time monitoring results of the molten pool state, forming a closed-loop control mechanism. This invention constructs a dual-field coupled flow synergistic control system, achieving simultaneous optimization of forming stability and microstructure refinement.

Description

Technical Field

[0001] This invention belongs to, but is not limited to, the field of laser cladding technology, and particularly relates to an energy field-assisted laser cladding process control method and system. Background Technology

[0002] Laser cladding is a surface strengthening and repair technology that uses a high-energy laser beam as a heat source to melt alloy powder or wire and rapidly solidify it to form a metallurgical bonded coating. It is widely used in aerospace, energy equipment, and high-end manufacturing. As application scenarios increasingly demand higher service reliability and microstructure uniformity, porosity defects, coarse grains, and elemental segregation problems that easily occur in traditional laser cladding processes are gradually becoming key factors restricting its further promotion.

[0003] To improve the flow state and solidification structure of the molten pool, related research has begun to introduce external field-assisted methods. One type of technique involves periodically oscillating a laser beam to generate lateral or rotational disturbances in the molten pool during scanning, thereby enhancing melt convection and mass transfer. Another type of technique applies alternating or constant electromagnetic fields during cladding, utilizing the Lorentz force generated in the conductive melt to drive the flow within the molten pool, thus suppressing porosity formation and refining grains. Building upon this, existing techniques have proposed coupling laser oscillation with electromagnetic fields to further enhance the molten pool stirring effect.

[0004] However, as the closest existing technology, the aforementioned combination of laser oscillation and electromagnetic assistance mainly focuses on matching or synchronizing the laser oscillation frequency with the electromagnetic field frequency, lacking precise control over the interaction of different force fields. In actual processing, due to the lack of stable constraints between the molten pool flow direction caused by laser oscillation and the electromagnetic force driving direction, the two may randomly superimpose or cancel each other in time or space, resulting in significant fluctuations in the stress state of the molten pool, unstable flow behavior, and even inducing periodic ripples or macroscopic forming defects.

[0005] Meanwhile, existing technologies typically employ a single method of controlling the stirring intensity. When the external field is increased to improve the internal density of the molten pool, the surface of the molten pool is prone to violent fluctuations and splashing, affecting the surface quality of the formed layer. Conversely, when the external field is reduced to ensure surface smoothness, it is difficult to effectively eliminate internal porosity and structural defects, making it difficult to simultaneously achieve both the intrinsic and surface quality of the cladding layer. Furthermore, in existing technologies, the flow effect generated by laser oscillation is mainly concentrated in the upper and middle regions of the molten pool, with limited effect on the deep melt at the bottom of the pool, making it difficult to effectively eliminate deep porosity and segregation zones.

[0006] Therefore, existing laser oscillation and electromagnetic assisted cladding technologies still generally suffer from problems such as disordered force field action, single control mode, and insufficient ability to improve deep defects, which urgently require a new technical solution. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a process optimization method and system for energy field-assisted and oscillating laser cladding.

[0008] The present invention is implemented as follows: an energy field-assisted laser cladding process control method, which simultaneously introduces a first melt flow induced by the periodic spatial motion of the laser and a second melt flow induced by the action of an alternating magnetic field into a conductive molten pool.

[0009] By controlling the vector direction relationship between the first melt flow and the second melt flow, the two flows can switch between at least two different cooperative states, thereby changing the synthetic flow structure inside the molten pool and achieving regulation of the stability or morphology of the molten pool.

[0010] Furthermore, the cooperative state includes:

[0011] An enhanced state in which two flow directions are aligned;

[0012] Shear disturbance state with periodic changes in two flow directions;

[0013] A state of inhibition where two flow directions are opposite.

[0014] Furthermore, the switching of the cooperative state is achieved by adjusting the frequency relationship between the alternating magnetic field frequency and the laser spatial motion frequency.

[0015] Furthermore, the switching of the cooperative state is achieved by adjusting the phase difference between the alternating magnetic field and the laser spatial motion.

[0016] This invention also provides a process optimization method for energy field-assisted and oscillating laser cladding. The process optimization method for energy field-assisted and oscillating laser cladding specifically includes:

[0017] Step S1: Substrate pretreatment and system initialization. Remove the oil and oxide layer from the substrate surface. Set the laser base power, scanning speed and powder feed rate according to the substrate material (magnetic / non-magnetic) and cladding powder characteristics.

[0018] Step S2: Defect-oriented process mode selection and parameter setting. Based on the processing target or the predicted defect type, select one of the three modes A, B, or C for cladding.

[0019] Step S3: Collaborative preheating. Before the formal powder feeding and cladding, a high-frequency current (induction heating mode) is output by an electromagnetic coil to preheat the substrate area to be clad in a non-contact manner.

[0020] Step S4: Dynamic closed-loop cladding, start laser light emission and powder feeding, the system works collaboratively according to the set mode (A / B / C);

[0021] Step S5: Electromagnetic composite post-processing. After the single-layer cladding is completed, keep the electromagnetic field on (stop the laser). Utilize the magnetostrictive effect and induced Joule heating generated by the low-frequency alternating magnetic field to perform in-situ annealing and oscillatory aging on the cladding layer in the red-hot state.

[0022] Furthermore, in step S2, the core control principle is fluid dynamics vector synthesis, as detailed below:

[0023] Establish a molten pool velocity vector model:

[0024] The drag force caused by the beam oscillation and the fluid velocity vector induced by the Marangoni effect;

[0025] : The velocity vector driven by the Lorentz force induced in the conductive melt by the changing magnetic field;

[0026] By controlling the frequency difference between the two ( ) and phase difference ( This enables three specific process modes.

[0027] Furthermore, Mode A is a synchronous and phase-integrated enhancement mode, which is suitable for materials with high porosity and high viscosity.

[0028] Control logic: Set the magnetic field frequency to equal the laser oscillation frequency ( And the phase difference (or a fixed small angle compensation set according to the melt hysteresis).

[0029] Vector synthesis effect: The direction of the Lorentz force is always consistent with the direction of the fluid motion induced by the laser scanning (angle < At this point, the modulus is maximized.

[0030] Furthermore, mode B is a differential frequency shearing fine-grain mode, which is suitable for materials with coarse grains and easy cracking.

[0031] Control logic: The magnetic field frequency is set to have a specific deviation from the laser oscillation frequency;

[0032] Vector synthesis effect: The angle between the direction of the Lorentz force and the direction of laser-induced flow changes rapidly over time (cycle).

[0033] Furthermore, mode C is a same-frequency, opposite-phase braking mode, which is suitable for poor forming, easy humps, and large surface ripples.

[0034] Control logic: Set the magnetic field frequency to equal the laser oscillation frequency ( ), and the phase difference is 180 degrees;

[0035] Vector synthesis effect: The direction of the Lorentz force is always opposite to the direction of the fluid motion induced by the laser scan. Therefore, it is weakened.

[0036] Furthermore, in step S4, if the visual sensor detects biting or a hump trend at the edge of the molten pool (due to excessive flow rate), the controller automatically switches to mode C or increases the intensity of the reverse magnetic field; if the thermal imager detects that the cooling rate is too fast (> If the magnetic field frequency is increased, the mode will automatically switch to mode B and the magnetic field frequency will be increased to enhance the grain refinement effect.

[0037] Another objective of this invention is to provide a process optimization system for energy field-assisted and oscillating laser cladding, the system specifically comprising:

[0038] The pretreatment module is used for substrate pretreatment and system initialization;

[0039] The process mode selection module is used to select one of three modes, A, B, or C, based on the processing target or the predicted defect type.

[0040] The induction heating module is used to output high-frequency current from an electromagnetic coil to preheat the substrate area to be clad in a non-contact manner, thereby reducing the temperature gradient between the substrate and the cladding layer.

[0041] The Mode A cladding module is used for cladding of materials with high porosity and high viscosity by selecting the same frequency and phase enhancement mode;

[0042] The Mode B cladding module is used to select the differential frequency shearing fine grain mode for cladding of materials with coarse grains and easy cracking.

[0043] The Mode C cladding module is used to select the same-frequency reverse-phase braking mode for cladding of materials with poor formability, easy hump, and large surface ripples.

[0044] The electromagnetic composite post-processing module is used to keep the electromagnetic field on after the single-layer cladding is completed. It utilizes the magnetostrictive effect and induced Joule heating generated by the low-frequency alternating magnetic field to perform in-situ annealing and oscillatory aging on the cladding layer in the red-hot state.

[0045] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0046] This invention focuses on the active construction and controllable reconstruction of the internal flow structure of a conductive molten pool. It proposes vector coupling between a first molten flow induced by the periodic spatial motion of a laser and a second molten flow generated by an alternating magnetic field. By controlling the directional relationship, frequency matching relationship, and phase difference between the two flows, switchable control between various synergistic states such as strengthening, shear disturbance, and suppression can be achieved. This overcomes the technical limitations of traditional laser cladding processes, which rely solely on single molten pool flow and are difficult to precisely intervene in. Compared to existing solutions that rely solely on heat input adjustment or a single electromagnetic stirring method, this invention, for the first time, constructs a programmable molten pool flow field structure from the perspective of flow vector synthesis. This enables the formation of a predictable and adjustable synthetic flow mode within the molten pool, improving molten pool stability, suppressing spatter and collapse, enhancing element diffusion and compositional uniformity, improving grain refinement and microstructure density, and significantly improving the mechanical properties and microstructure consistency of the cladding layer. Simultaneously, a closed-loop collaborative control mechanism based on real-time monitoring of the molten pool state is introduced. This mechanism can dynamically switch collaborative states according to edge flow anomalies, cooling rate changes, or microstructure evolution trends, achieving a shift from "parameter-preset control" to "state-adaptive control," thus improving process robustness and repeatability. Combined with an energy field-assisted heating unit, in-situ thermal regulation and stress release can also be achieved, further optimizing microstructure performance matching. Overall, this invention achieves active configuration control at the flow mechanism level and closed-loop collaborative optimization at the control strategy level, demonstrating significant technological advancements and engineering application value.

[0047] This invention achieves deterministic control of molten pool flow through "phase locking" and "vector synthesis" techniques. The specific advantages are analyzed below:

[0048] (1) Eliminate "force field chaos" and achieve deterministic molten pool flow control:

[0049] Principle: In existing technologies, the laser oscillation frequency and the alternating magnetic field frequency are often set independently, causing the angle between the flow field vectors generated by the two to vary randomly, resulting in uncontrollable "beat frequency" interference. This invention introduces phase-locked loop (PLL) control to force... Or maintain a fixed frequency difference.

[0050] Beneficial effects: It eliminates random turbulence and kinetic energy cancellation phenomena inside the molten pool, ensuring that the stress on the molten pool is predictable and repeatable every millisecond, greatly improving the stability and repeatability of the process, and is particularly suitable for the repair of high value-added parts such as aero-engine blades.

[0051] (2) Mode A (Same frequency and phase) - Deep exhaust, greatly reducing porosity:

[0052] Principle: The mechanical drag force generated by the laser oscillation is vector-superimposed with the Lorentz force of the electromagnetic field in time and space. When the two are in phase, a resonance effect is formed, and the fluid velocity exceeds the limit of a single energy field.

[0053] Beneficial effects: This "high-torque" stirring can penetrate the shallow region dominated by surface tension, reaching the bottom of the molten pool and rapidly drawing in tiny bubbles trapped deep within to the surface for escape. Compared to traditional oscillating lasers, the porosity can be further reduced to below 0.05%, solving the problem of difficult deep degassing in high-viscosity materials (such as Ni60).

[0054] (3) Mode B (differential frequency shearing) – powerfully breaks dendrites, solving hot cracks and coarse grains:

[0055] Principle: Utilizing the frequency difference between the two ( A high-frequency alternating shear flow field is created inside the molten pool. The resultant force direction is... The rapid rotation at a certain frequency applies a periodic mechanical breaking force to the columnar crystal tips at the solid-liquid interface.

[0056] Beneficial effects: This shearing action breaks down coarse columnar grains more efficiently than simple ultrasound or steady-state magnetic fields, transforming them into fine equiaxed grains, thus significantly increasing the nucleation rate. For difficult-to-weld high-temperature alloys such as Inconel 738, it can effectively suppress liquefaction cracks and crystallization cracks, greatly improving the mechanical properties of the joint.

[0057] (4) Mode C (same frequency, opposite phase) - active magnetic damping to achieve "mirror" shaping:

[0058] Principle: Utilizing vector subtraction ( The principle is as follows: When the high-speed oscillation of the laser beam generates an excessive centrifugal tendency that causes molten material to splash or hump, the inverse Lorentz force provides an instantaneous "electromagnetic braking" force.

[0059] Beneficial effects: It actively suppresses violent fluctuations on the surface of the molten pool, preventing the formation of hump weld beads. Compared with traditional passive braking by a steady-state magnetic field, this active reverse-phase braking has a faster response speed and is more targeted, enabling the production of a smooth surface with extremely low Ra value even at high-speed cladding (>15mm / s), reducing subsequent machining allowances.

[0060] This invention addresses key bottlenecks in laser cladding processes, such as molten pool flow instability, venting difficulties, and susceptibility to hot cracking. It proposes a "phase- and frequency-locked vector synthesis control" approach to achieve spatiotemporal coordinated regulation of the laser oscillation trajectory and alternating magnetic field, constructing a controllable electromagnetic-thermal-fluid multi-field coupling adjustment mechanism. In terms of technology transfer, this solution significantly expands the material applicability of laser cladding remanufacturing, enabling stable application to traditionally difficult-to-clad materials such as high-viscosity alloys and easily cracked high-temperature alloys, providing a process foundation for the remanufacturing of high-end components. By introducing an "electromagnetic braking" effect to actively suppress molten pool fluctuations, near-net-shape forming is achieved under high-speed cladding conditions, reducing surface roughness and subsequent machining allowances, and improving forming consistency and yield.

[0061] To address the challenge of venting deep-melt pools, this invention utilizes a resonant stirring effect created through in-phase and frequency-enhanced mixing to promote the escape of deep gases. To address the challenge of controlling hot cracking in high-temperature alloys, it employs a high-frequency shear flow field to break dendrites and refine the grain structure, thereby suppressing hot crack formation at its source. This technology can serve as a core add-on module for high-end laser cladding equipment or an intelligent upgrade solution for existing production lines, targeting high-value-added fields such as aerospace, energy equipment, and precision mold repair, demonstrating significant industrialization potential and long-term commercial value. Attached Figure Description

[0062] Figure 1 This is a flowchart of the process optimization method under energy field-assisted and oscillating laser cladding provided in the embodiments of the present invention;

[0063] Figure 2 This is a block diagram of the process optimization system under energy field-assisted and oscillating laser cladding provided in an embodiment of the present invention;

[0064] Figure 3 This is a schematic diagram of the device provided in an embodiment of the present invention;

[0065] Figure 4 This is a front view of the device provided in an embodiment of the present invention;

[0066] In the diagram: 1. Galvanometer system; 2. Focusing unit; 3. Electromagnet; 4. Six-axis laser; 5. Worktable. Detailed Implementation

[0067] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0068] The technical solution provided by this invention does not simply superimpose laser oscillation technology and alternating magnetic field technology, but rather constructs an overall process system around the vector-coordinated control mechanism of fluid movement within the molten pool. Its core lies in the dynamic coupling relationship between the flows induced by the two physical fields and their controllable switching logic. Specifically, during laser cladding, the periodic spatial motion of the laser causes the heat source to migrate in a controlled manner within the molten pool, forming a directional temperature gradient and surface tension gradient distributed along the scanning trajectory, thereby inducing the formation of a first melt flow. Simultaneously, an alternating magnetic field is applied to the conductive melt, and the interaction between the induced current and the magnetic field generates a Lorentz force, forming a second melt flow. The two flows originate from different physical driving mechanisms, and their direction, frequency, and intensity can be independently adjusted. This invention is not limited to enhancing or weakening either single flow, but rather coordinates and controls the vector direction relationship between the two, allowing the synthesized flow field to actively switch between different synergistic states such as enhanced stirring, periodic shearing, or flow suppression. Since the molten pool flow structure directly determines the gas discharge path, solidification interface morphology, and grain growth direction, vector-coordinated control can achieve simultaneous optimization of forming stability and microstructure refinement.

[0069] In a preferred embodiment, predictable switching of the flow vector is achieved by adjusting the matching relationship between the alternating magnetic field frequency and the laser spatial motion frequency, as well as the phase difference between them. When the two flow directions are consistent, a synthetic enhanced flow field is formed inside the molten pool, enhancing convective heat transfer and gas escape; when the two flow directions are opposite, the synthetic flow is weakened, which helps to suppress excessive disturbance at the edge of the molten pool and improve forming stability; when a periodic directional change occurs between the two, an alternating shear flow field is formed inside the molten pool, which helps to interrupt columnar crystal growth and promote grain refinement. This synergistic relationship is not a simple parameter superposition, but an overall control logic established based on the coupling effect of fluid dynamics and electromagnetic force. It must be implemented synchronously within the same molten pool to form the above-mentioned flow field structure. Even if existing technologies disclose laser oscillation or magnetic field-assisted cladding separately, they are limited to the enhanced application of a single physical field and do not involve the vector synergistic control and state switching mechanism between the two induced flows, nor do they establish a closed-loop switching logic based on molten pool state feedback. Therefore, it is difficult to obtain the overall flow field control effect achieved by this invention through a simple combination of technologies. This invention achieves the active construction and real-time transformation of the molten pool flow structure through a holistic mechanism, enabling different process objectives to be dynamically realized in the same system, resulting in significant overall technical effects and inventiveness.

[0070] like Figure 1 As shown, this embodiment of the invention provides a process optimization method under energy field-assisted and oscillating laser cladding, the method specifically including:

[0071] Step S1: Substrate pretreatment and system initialization, remove oil and oxide layer from the substrate surface, and set the laser base power, scanning speed and powder feeding rate according to the substrate material and cladding powder characteristics;

[0072] Step S2: Defect-oriented process mode selection and parameter setting. Based on the processing target or the predicted defect type, select one of the three modes A, B, or C for cladding.

[0073] Step S3: Collaborative preheating. Before the formal powder feeding and cladding, a high-frequency current is output by an electromagnetic coil to preheat the substrate area to be clad in a non-contact manner, thereby reducing the temperature gradient between the substrate and the cladding layer.

[0074] Step S4: Dynamic closed-loop cladding, start laser light emission and powder feeding, and the system works in coordination according to the set mode.

[0075] Step S5: Electromagnetic composite post-processing. After the single-layer cladding is completed, the electromagnetic field is kept on. The magnetostrictive effect and induced Joule heating generated by the low-frequency alternating magnetic field are used to perform in-situ annealing and oscillatory aging on the cladding layer in the red-hot state, which promotes dislocation rearrangement and releases residual stress.

[0076] The process optimization method for energy field-assisted and oscillating laser cladding proposed in this invention is not a simple superposition of existing laser cladding, electromagnetic-assisted heating, or post-processing technologies. Instead, it constructs a coordinated control mechanism for the entire process of "heat source - flow field - microstructure - stress" under a unified control architecture. Its core lies in achieving continuous physical field reconstruction before, during, and after cladding through phase- and frequency-controllable energy field coupling, so that each step forms a causal closed loop and a temporal progression relationship, which is different from the splicing combination of existing technologies in terms of overall mechanism.

[0077] In step S1, substrate pretreatment and system initialization are not just routine preparation processes, but rather establish a unified parameter benchmark for subsequent electromagnetic field coupling and laser energy input. Based on the substrate's conductivity, permeability, and cladding powder flow characteristics, the system presets the laser base power, scanning speed, and powder feed rate, and simultaneously calculates the output frequency window of the electromagnetic coil, ensuring that the subsequent energy field matches the molten pool size and flow characteristics, thus forming the prerequisite for physical field coupling.

[0078] The defect-oriented mode selection in step S2 is the decision-making center of the overall mechanism of this invention. Modes A / B / C are preset with different magnetic field frequency ranges and oscillation amplitude combinations for different target defects such as porosity-dominant, crack-sensitive, or coarsening tendency, allowing the magnetic field action mode to switch between "flow-enhancing," "shear-refining," or "stress-controlled" modes. This mode selection is not a single parameter adjustment, but a coordinated control strategy linking the laser oscillation phase, electromagnetic frequency, and power output, enabling the system to enter a targeted control state before processing.

[0079] The synergistic preheating in step S3 uses high-frequency current to achieve non-contact induction heating, establishing a gradual temperature gradient before powder feeding, so that the temperature difference field between the substrate and the molten pool to be formed is reconstructed in advance. This preheating process is not isolated from the subsequent cladding, but rather achieves a smooth transition of heat input by controlling the continuous transition between the preheating frequency and the subsequent molten pool stirring frequency, thereby reducing thermal shock and stress concentration from the source.

[0080] Step S4 is the dynamic closed-loop cladding stage. The laser oscillation and alternating magnetic field achieve a locked relationship on the time axis. The electromagnetic field generates a directional Lorentz force on the molten pool, forming a controllable flow structure. Simultaneously, the oscillating laser alters the molten pool morphology, giving the magnetic field's driving effect on the fluid spatial selectivity. These two elements reinforce each other, forming a stable internal circulation and a high-frequency shear flow field, enabling simultaneous degassing enhancement and dendrite fragmentation. This stage uses temperature and current feedback to fine-tune the power, maintaining the molten pool flow state within the target range, thus constituting true multi-field closed-loop control, rather than single-field superposition.

[0081] Step S5, the electromagnetic composite post-treatment, continues the aforementioned energy field control logic. While the cladding layer is still red-hot, a low-frequency alternating magnetic field is applied to utilize the combined effects of magnetostrictive vibration and induced Joule heating for in-situ annealing and oscillatory aging. This post-treatment is not an independent process but rather forms a stepwise transition with the previous stirring frequency, allowing the internal structure to smoothly transition from a dynamically refined state to a stress-released state, achieving continuous control over dislocation rearrangement and residual stress reduction.

[0082] This invention utilizes frequency-phase-power coupling control within a unified control framework to create an integrated energy field control chain encompassing preheating, cladding, and post-processing. Each step exhibits physical continuity and functional complementarity, establishing a systematic working principle of multi-field synergy and full-process control. Even if existing technologies separately disclose laser oscillation, electromagnetic assistance, or annealing treatments, they cannot achieve the aforementioned timing locking and synergistic effect through simple combinations, thus hindering the effective derivation of the overall solution of this invention.

[0083] The core control principle of step S2 is fluid dynamics vector synthesis, as detailed below:

[0084] Establish a molten pool velocity vector model:

[0085] The drag force caused by the beam oscillation and the fluid velocity vector caused by the Marangoni effect.

[0086] The velocity vector driven by the Lorentz force induced in the conductive melt by the changing magnetic field.

[0087] By controlling the frequency difference between the two ( ) and phase difference ( ), to achieve the following three specific process modes.

[0088] Mode A: Same frequency and phase enhancement mode, for materials with high porosity and high viscosity.

[0089] Control logic: Set the magnetic field frequency to equal the laser oscillation frequency ( And the phase difference (or a fixed small angle compensation set according to the melt hysteresis).

[0090] Vector synthesis effect: The direction of the Lorentz force is always consistent with the direction of the fluid motion induced by the laser scanning (angle < At this point, the modulus is maximized.

[0091] Technical effects: It generates strong directional resonance stirring, the flow rate of the molten pool exceeds the critical value, forming a molten pool with a larger depth-to-width ratio, which rapidly entrains the tiny bubbles trapped in the depth to the surface and escapes, significantly reducing porosity and increasing density.

[0092] Mode B: Differential frequency shearing fine grain mode, for materials with coarse grains and easy cracking.

[0093] Control logic: The magnetic field frequency is set to have a specific deviation from the laser oscillation frequency.

[0094] Vector synthesis effect: The angle between the direction of the Lorentz force and the direction of laser-induced flow changes rapidly over time (cycle).

[0095] Technical effect: High-frequency disturbances occur in the flow field inside the molten pool, generating severe shear stress. This shear force acts on the columnar crystal tips at the solid-liquid interface, mechanically fracturing them. The fractured crystal arms then detach into the melt, becoming non-spontaneous nucleation sites, thereby inhibiting columnar crystal growth, promoting equiaxed crystal formation, refining grains, and reducing hot cracking.

[0096] Mode C: Same frequency, opposite phase braking mode, designed for materials with poor forming quality, easy humps, and large surface ripples.

[0097] Control logic: Set the magnetic field frequency to equal the laser oscillation frequency ( ), and the phase difference is 180 degrees.

[0098] Vector synthesis effect: The direction of the Lorentz force is always opposite to the direction of the fluid motion induced by the laser scan. Therefore, it is weakened.

[0099] Technical effect: namely, the "dynamic electromagnetic braking" effect. When the laser oscillates at high speed, especially at high power and high scanning speed, the melt tends to accumulate backward due to inertia, forming a "hump". The inverse Lorentz force provides an instantaneous damping force to counteract the fluid inertia, suppress violent shaking of the molten pool surface, make the cladding layer surface smooth and clean, and reduce edge biting.

[0100] In step S4, if the visual sensor detects biting or a hump trend at the edge of the molten pool (due to excessive flow rate), the controller automatically switches to mode C or increases the intensity of the reverse magnetic field; if the thermal imager detects that the cooling rate is too fast (> If the magnetic field frequency is increased, the mode will automatically switch to mode B and the magnetic field frequency will be increased to enhance the grain refinement effect.

[0101] like Figure 2 As shown in the figure, the process optimization system under energy field-assisted and oscillating laser cladding provided by the embodiments of the present invention specifically includes:

[0102] The pretreatment module is used for substrate pretreatment and system initialization;

[0103] The process mode selection module is used to select one of three modes, A, B, or C, based on the processing target or the predicted defect type.

[0104] The induction heating module is used to output high-frequency current from an electromagnetic coil to preheat the substrate area to be clad in a non-contact manner, thereby reducing the temperature gradient between the substrate and the cladding layer.

[0105] The Mode A cladding module is used for cladding of materials with high porosity and high viscosity by selecting the same frequency and phase enhancement mode;

[0106] The Mode B cladding module is used to select the differential frequency shearing fine grain mode for cladding of materials with coarse grains and easy cracking.

[0107] The Mode C cladding module is used to select the same-frequency reverse-phase braking mode for cladding of materials with poor formability, easy hump, and large surface ripples.

[0108] The electromagnetic composite post-processing module is used to keep the electromagnetic field on after the single-layer cladding is completed. It utilizes the magnetostrictive effect and induced Joule heating generated by the low-frequency alternating magnetic field to perform in-situ annealing and oscillatory aging on the cladding layer in the red-hot state.

[0109] The energy field-assisted and oscillating laser cladding process optimization system provided in this embodiment of the invention achieves full-process coordination of heat input, melt pool flow, microstructure evolution and residual stress control under a unified control platform. Its working principle is reflected in the stage coupling and patterned control of multi-physics fields.

[0110] During system operation, the preprocessing module first cleans the substrate surface, removes oil and oxide layers, and initializes parameters based on the substrate's conductivity, magnetic permeability, and cladding powder characteristics, establishing a baseline operating condition for subsequent energy field matching. The process mode selection module, based on the processing target or predicted defect type, calls the parameter sets of the corresponding modes A / B / C to establish a preset coupling state between the laser oscillation frequency, amplitude, and electromagnetic field frequency and phase relationship.

[0111] Before the powder is fed, the induction heating module outputs a high-frequency current, which generates induced eddy currents and Joule heat on the surface of the substrate through an electromagnetic coil. This achieves non-contact rapid preheating, reconstructs the temperature field on the substrate surface, reduces the thermal gradient and thermal shock during the cladding process, and creates thermal conditions for the formation of a stable molten pool.

[0112] After entering the cladding stage, the system executes different energy field coupling mechanisms according to the selected mode: In mode A, the electromagnetic field and laser oscillation are in phase and frequency, which enhances convection and stirring inside the molten pool, promotes gas escape, and improves the problem of difficult exhaust of high viscosity materials; In mode B, a high-frequency shear flow field is formed by differential frequency control, which breaks dendrites, refines grains, and reduces the tendency of hot cracking; In mode C, the same frequency and opposite phase control is used to form an "electromagnetic braking" effect, which suppresses surface fluctuations of the molten pool and excessive metal flow, and improves forming stability and surface quality.

[0113] After the single-layer cladding is completed, the electromagnetic composite post-processing module continuously applies a low-frequency alternating magnetic field, generating magnetostrictive vibration and induced Joule heating in the red-hot state of the cladding layer. This achieves in-situ annealing and oscillatory aging, promoting dislocation rearrangement and residual stress release. Through the above continuous control, the modules form a closed loop connection in terms of time and physical mechanisms, resulting in an overall improvement in cladding quality, microstructure, and forming stability.

[0114] The apparatus provided in the embodiments of the present invention is as follows: Figure 3 , Figure 4 As shown. Figure 3 and Figure 4 As shown, the energy field-assisted and oscillating laser cladding device of this embodiment mainly includes a galvanometer system 1, a focusing unit 2, an electromagnet 3, a six-axis laser 4, and a worktable 5. The six-axis laser 4 is installed at the end of a multi-degree-of-freedom robotic arm, enabling spatial attitude adjustment and path following, and is used to output a high-energy laser beam; the galvanometer system 1 is set in the laser optical path, used to perform high-speed oscillating scanning of the laser beam, achieving controllable energy distribution adjustment of the trajectory; the focusing unit 2 is located after the galvanometer system, used to precisely focus the oscillating modulated laser beam, so that the spot size matches the molten pool size; the electromagnet 3 is arranged below the worktable 5 or near the cladding area, used to apply an adjustable alternating magnetic field during the cladding process; the worktable 5 is used to support the substrate to be processed and can cooperate to achieve translational or rotational movements.

[0115] Its working principle is as follows: The six-axis laser 4 adjusts its spatial attitude under the command of the control system, causing the laser beam to oscillate with a set frequency and amplitude through the galvanometer system 1. Subsequently, it forms a stable molten pool on the substrate surface through the focusing unit 2. Simultaneously, an alternating current is passed through the electromagnet 3, creating a time-varying magnetic field in the molten pool region. The molten metal generates a Lorentz force under the influence of the magnetic field, inducing a controllable flow structure within the molten pool. The oscillation of the galvanometer changes the molten pool morphology and flow boundary conditions, while the electromagnetic field regulates the internal flow intensity and direction. These two elements work synergistically to control the stability of the molten pool, gas discharge, and grain growth behavior. Through the relative coordination between the robotic arm movement and the worktable 5, high-quality cladding processing of complex spatial curved surfaces or multi-angle components can be completed.

[0116] This invention provides three typical process modes: same-frequency enhancement, differential frequency shearing, and reverse-phase braking. The implementation process and comparative effects are described in detail below with reference to specific material systems.

[0117] Example 1: Preparation of "crack-free, ultrafine-grained" Ni60 high-hardness alloy coating, corresponding to mode B: differential frequency shear fine-grained mode.

[0118] Application background: Ni60 alloy has high hardness (>60CrC), but it is very prone to penetrating cracks due to large temperature gradients in conventional laser cladding, and its microstructure is mostly coarse oriented columnar crystals.

[0119] Experimental conditions:

[0120] Substrate: 45 steel plate; Cladding powder: Ni60 self-fluxing alloy powder (particle size 45-105μm).

[0121] Laser system: fiber laser, power Spot diameter .

[0122] Table 1 Comparison of Process Parameter Settings

[0123]

[0124] Implementation process of this invention:

[0125] Set the laser oscillation frequency This generates a mechanically stirred flow field. .

[0126] Set excitation current frequency This generates an alternating Lorentz force flow field. .

[0127] The two form The difference frequency beat frequency. Inside the molten pool, the direction of the resultant force vector rotates and changes 50 times per second, generating dynamic shear stress in all directions on the dendrites at the solid-liquid interface.

[0128] Comparison of implementation results data:

[0129] Microstructure (grain size):

[0130] Comparative Example 1: Coarse columnar crystals, average grain size .

[0131] Comparative Example 2: The grains are refined, but still have directionality.

[0132] This invention: columnar crystals are completely broken down and transformed into fine equiaxed crystals throughout the entire grain, reducing the average grain size to... (The process is refined by about 75%).

[0133] Mechanism support: Regarding the theory of "force field breaking dendrites", the difference frequency shear maximizes this effect.

[0134] Crack sensitivity:

[0135] Comparative Example 1: 3 to 5 transverse cracks are visible on the surface.

[0136] This invention: Dyeing flaw detection reveals zero cracks. The combined effect of fine grain strengthening and uniform elemental distribution (suppressing brittle phase segregation) eliminates crack initiation points.

[0137] Microhardness:

[0138] Comparative Example 1: Average ~630HV.

[0139] This invention: average ~920HV (a further improvement over the 852HV assisted by steady-state magnetic field).

[0140] Example 2: "Deep venting and densification" of Inconel 738 hard-to-weld superalloy, corresponding to mode A: in-phase enhancement mode.

[0141] Application Background: Inconel 738 is a difficult-to-weld material with high melt viscosity, making it prone to micropores and incomplete fusion defects. Simply relying on laser oscillation is insufficient to reach the bottom of the molten pool.

[0142] Experimental conditions:

[0143] Substrate: Inconel 718; Cladding powder: Inconel 738.

[0144] Process parameter settings (vector synthesis):

[0145] Laser oscillation: linear reciprocating oscillation, frequency (high frequency).

[0146] Magnetic field coordination: alternating magnetic field frequency .

[0147] Phase control: The phase difference is controlled via a phase-locked loop. .

[0148] Physical meaning: When the laser beam oscillates to the left, inducing the fluid to flow to the left, the Lorentz force also pushes the fluid to the left. Resultant velocity. It has reached its maximum value.

[0149] Implementation results:

[0150] Molten pool morphology: The melting depth is increased by about 25% compared to when there is no magnetic field, and the depth-to-width ratio is increased, which solves the problem of "shallow molten pool" usually caused by laser oscillation.

[0151] Porosity:

[0152] Normal oscillation: 1.2% (small pores make it difficult to escape).

[0153] This invention (same frequency enhancement): <0.05% (nearly fully dense).

[0154] Mechanism verification: Based on the flow field simulation in the reference, the enhanced Lorentz force overcomes the fluid viscous resistance at the bottom, constructs a strong convection ring that runs through the top and bottom of the molten pool, and rapidly carries deep bubbles to the surface to escape.

[0155] Example 3: "Mirror" forming control under high-speed cladding, corresponding to mode C: same frequency reverse phase braking mode

[0156] Application Background: To improve processing efficiency, high scanning speeds are employed ( When cladding is performed, the molten material has a large backflow inertia, which easily forms a "hump" weld bead and causes severe surface ripples.

[0157] Process parameter settings (vector synthesis):

[0158] Scanning speed: (high speed).

[0159] Laser oscillation: Figure-eight oscillation, frequency .

[0160] Magnetic field coordination: alternating magnetic field frequency .

[0161] Phase control: Locking in phase difference (Inverted phase).

[0162] Physical significance: When the laser oscillation causes the melt to sway violently, the opposite Lorentz force acts as an "electromagnetic damper," counteracting the lateral and longitudinal inertial momentum of the fluid in real time.

[0163] Implementation results:

[0164] Surface roughness (Ra):

[0165] Field-free high-speed cladding: (The surface exhibits distinct fish-scale patterns and camel humps).

[0166] Steady-state magnetic field assistance: .

[0167] This invention (reverse phase braking): The cladding layer has a mirror-like gloss, which can meet some assembly requirements without subsequent grinding.

[0168] Geometric consistency: The cladding layer width fluctuation rate is controlled within ±2%, the edges are straight, and there is no biting.

[0169] Example 1: Example of Co-directional Synergistic Enhanced Stirring in High Viscosity Alloy Cladding

[0170] High-viscosity alloy powder with poor molten pool flowability was selected as the cladding material for laser cladding treatment of the steel substrate surface. During the cladding process, the laser beam scanned in a periodic oscillating manner, forming a directional flow along the scanning direction in the molten pool. Simultaneously, an alternating magnetic field that varied synchronously with the laser oscillation rhythm was applied to the molten pool region, generating a stable Lorentz force in the conductive melt to drive the flow.

[0171] By controlling the direction of the magnetic field-induced flow to be consistent with that of the laser-induced flow, the two flows superimpose within the molten pool, forming a reinforced composite flow structure. This synergistic effect significantly enhances the convection intensity within the molten pool, promoting gas escape and uniform mixing of the melt. The number of pores within the cladding layer is significantly reduced, and the density of the microstructure is significantly improved, verifying the effectiveness of co-directional synergistic vector control in improving the cladding quality of high-viscosity materials.

[0172] Example 2: Densification Control of Materials with High Porosity Tendency

[0173] For cladding powder materials prone to porosity, an alternating magnetic field is introduced to participate in molten pool control under the same laser oscillation cladding conditions. The laser oscillation induces periodic flow in the melt, and the magnetic field induces current in the molten pool, generating an auxiliary flow driven by the Lorentz force.

[0174] By maintaining the long-term alignment of the magnetic field-induced flow and the laser-induced flow, a stable and continuous fluid transport path is formed within the molten pool. This flow structure effectively prolongs the residence time of gas in the high-temperature zone of the melt, significantly improving gas flotation and discharge efficiency. The cross-section of the cladding layer shows a significant reduction in porosity, and the cladding channel morphology is uniform and continuous, demonstrating the technical advantages of the vector synergistic enhancement mechanism in porosity suppression.

[0175] Example 3: Differential Shear Refinement of Coarse-Grained Alloys

[0176] Laser cladding is performed using alloy materials that readily form coarse columnar crystals. During the cladding process, the laser beam oscillates to induce directional flow, while an alternating magnetic field is applied, causing the direction of the magnetic field-induced flow relative to the laser-induced flow to change periodically over time.

[0177] Under these conditions, a constantly changing angle forms between the two flows within the molten pool, resulting in an alternating shear flow field inside the pool. This shearing action continuously disturbs the solidification front, inhibiting preferential grain growth and promoting multidirectional nucleation. Experimental results show that the grain size of the cladding layer is significantly reduced, and the microstructure transforms from coarse columnar crystals to fine equiaxed crystals, fully demonstrating the innovative effect of differential vector synergy in grain refinement.

[0178] Example 4: Optimization of the solidification structure of easily cracked materials

[0179] For materials sensitive to thermal cracking, a magnetic field is introduced to assist in the control of the laser oscillating cladding process. By controlling the periodic change in the relative direction between the magnetic field-induced flow and the laser-induced flow, the flow state within the molten pool is kept under unsteady shear conditions.

[0180] This flow state effectively reduced the concentration of temperature gradients within the molten pool and mitigated stress concentration during solidification. The microstructure of the cladding layer showed uniform grain distribution and a significant reduction in crack initiation, indicating that regulating the solidification behavior of the molten pool based on flow vector relationships can reduce the risk of crack formation at a mechanistic level.

[0181] Example 5: Reverse Braking Example for Unstable Molding Channels

[0182] During the cladding process, when the laser oscillation induces a large flow velocity and metal accumulation tends to appear at the edge of the molten pool, the alternating magnetic field is adjusted to make the magnetic field-induced flow direction opposite to the laser-induced flow direction.

[0183] At this point, the two flows cancel each other out within the molten pool, weakening the overall flow intensity and effectively controlling the molten pool metal spreading rate. The surface ripples of the cladding channel are significantly reduced, the hump phenomenon is suppressed, and the surface smoothness of the cladding layer is significantly improved, verifying the unique role of reverse vector cooperation in forming stability control.

[0184] Example 6: Dynamic Switching Based on Molten Pool State Feedback

[0185] During continuous multi-pass cladding, the synergistic relationship between magnetic field-induced flow and laser-induced flow is dynamically adjusted by monitoring the morphology and temperature changes of the molten pool in real time. When the molten pool flow is detected to be too fast, the system automatically adjusts to a reverse synergistic state to suppress the flow; when the cooling rate is detected to be too fast, it adjusts to a shear synergistic state with periodic directional changes to enhance grain refinement.

[0186] This dynamic control method enables the on-demand switching of different flow mechanisms in the same cladding process, which simultaneously optimizes the cladding layer in terms of forming quality, microstructure refinement and internal density, demonstrating the comprehensive technical advantages of the vector collaborative control mechanism under complex working conditions.

[0187] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for controlling laser cladding process with energy field assistance, characterized in that, In a conductive molten pool, a first melt flow induced by the periodic spatial motion of a laser and a second melt flow induced by an alternating magnetic field are simultaneously introduced. By controlling the vector direction relationship between the first melt flow and the second melt flow, the two flows can switch between at least two different cooperative states, thereby changing the synthetic flow structure inside the molten pool and achieving regulation of the stability or morphology of the molten pool.

2. The method as described in claim 1, characterized in that, The cooperative state includes: An enhanced state in which two flow directions are aligned; Shear disturbance state with periodic changes in two flow directions; A state of inhibition where two flow directions are opposite.

3. The method as described in claim 1, characterized in that, The switching of the cooperative state is achieved by adjusting the frequency relationship between the alternating magnetic field frequency and the laser spatial motion frequency.

4. The method as described in claim 1, characterized in that, The switching of the cooperative state is achieved by adjusting the phase difference between the alternating magnetic field and the laser spatial motion.

5. A laser cladding collaborative control method based on molten pool state feedback, characterized in that, During the execution of the method described in claim 1, the state of the molten pool is monitored in real time; Based on the monitoring results, determine whether the molten pool is in a state of intensified demand or stable demand. Based on the judgment result, the vector relationship between the first melt flow and the second melt flow is dynamically changed, so that the melt pool flow structure automatically switches between different cooperative states, thereby forming a closed-loop control.

6. The method as described in claim 5, characterized in that, When abnormal flow is detected at the edge of the molten pool, the cooperative state is switched from the strengthening state to the suppression state.

7. The method as described in claim 5, characterized in that, When excessively rapid cooling or a coarsening trend in the tissue is detected, the cooperative state is switched from a stable state to a shear perturbation state.

8. A cladding control system for implementing the method of any one of claims 1 to 7, characterized in that, include: The first flow induction unit is used to form a first melt flow in the molten pool along the spatial periodic motion direction; The second flow induction unit is used to apply an alternating magnetic field to the molten pool region to form a second melt flow; The control unit is used to adjust the vector relationship between the first melt flow and the second melt flow, so that the two switch between different cooperative states.

9. The system as described in claim 8, characterized in that, The control unit adjusts the vector relationship in real time based on the molten pool status monitoring results.

10. The system as described in claim 8, characterized in that, It also includes an energy field-assisted heating unit, which is used to perform electromagnetic heating or in-situ heat treatment on the cladding area before or after cladding.

Images