A laser-assisted beam-steered directed energy deposition manufacturing method

Abstract

The application discloses a laser-assisted light beam swing directional energy deposition manufacturing method, comprising the following steps: adopting an auxiliary laser head to tilt and output a first light spot to form a current machining interval, the current machining interval is sequentially divided into a first region, a second region and a third region along a deposition direction, and the energy density decreases from the first region to the third region; adopting a main laser head to output a second light spot, and controlling the second light spot to scan in the current machining interval according to a preset swing track to realize deposition; when the main laser head moves to a preset trigger position, the first light spot is controlled to jump to a next machining interval along the deposition direction. The first light spot is arranged to expand along a deposition path, and is cooperated with a swing deposition process in a manner of partition residence and trigger jump, so that the surface quality, the density and the forming stability of a deposition layer are improved.

Description

Technical Field

[0001] This invention relates to the field of oscillating laser deposition technology, and more particularly to a laser-assisted oscillating directional energy deposition manufacturing method. Background Technology

[0002] Laser Directed Energy Deposition (LDED) technology boasts advantages such as high forming efficiency, high material utilization, and suitability for near-net-shape forming of complex structures. To address issues like concentrated heat sources, coarse columnar crystals, and mechanical anisotropy in conventional LDED processes, oscillating laser scanning has been introduced into the deposition process. This method periodically controls the laser trajectory to expand the heat source's effective range, enhance flow behavior within the molten pool, and improve temperature field distribution, thereby increasing microstructure uniformity and forming quality. However, as the oscillation frequency increases, the local dwell time of the main laser heat source during the lateral reciprocating motion shortens in high-frequency oscillating LDED, reducing the effective thermal coupling time between powder particles and the molten pool. This can easily lead to incomplete melting of some powder particles, resulting in unmelted particles, localized undermelting, surface roughness, and shallow defects on the deposition channel surface and at the edge of the oscillation trajectory. Meanwhile, the oscillating scan causes the molten pool boundary and temperature field to change continuously. In particular, under-melted cold areas and local areas with insufficient heat are more likely to form on both sides of the oscillating trajectory envelope area and the trailing edge area. Insufficient preheating of the area to be deposited and insufficient remelting of the already deposited area make it difficult to further improve the interlayer bonding quality and surface quality, and further induce problems such as porosity, bubbles, microcracks and unstable interlayer bonding. Summary of the Invention

[0003] To address the technical problems existing in the background art, this invention proposes a laser-assisted beam oscillation directional energy deposition manufacturing method, comprising: An auxiliary laser head is tilted to output a first light spot to form the current processing area. The current processing area is divided into a first region, a second region, and a third region along the deposition direction, and the energy density decreases sequentially from the first region to the third region. The main laser head outputs a second spot, and controls the second spot to scan within the current processing area according to a preset swing trajectory to achieve deposition; wherein, the first spot is a strip with a long side and a short side, the long side is arranged along the deposition direction, and the short side covers the swing trajectory envelope of the second spot; When the main laser head moves to the preset trigger position, it controls the first laser spot to jump to the next processing zone along the deposition direction.

[0004] Furthermore, the step size P of the first spot jumping along the deposition direction and the length L of the first spot along the deposition direction satisfy: L - P ≥ L3, where L3 is the length of the third region of the current processing interval along the deposition direction.

[0005] Furthermore, the preset trigger position is located in the second region of the current processing zone. When the main laser head moves to the preset trigger position, the first light spot is controlled to move along the deposition direction, so that the front end of the first light spot along the deposition direction and the main laser head arrive at the starting point of the third region of the current processing zone at the same time.

[0006] Furthermore, the length ratio of the first region, the second region, and the third region along the deposition direction is 2:3:2.

[0007] Furthermore, the preset trigger position is located in the second region of the current processing zone. When the main laser head moves to the preset trigger position, the first light spot is controlled to jump along the deposition direction, so that when the main laser head reaches the starting point of the third region of the current processing zone, the front end of the first light spot along the deposition direction simultaneously reaches the starting point of the second region of the current processing zone.

[0008] Furthermore, the length ratio of the first region, the second region, and the third region along the deposition direction is 1:1:1.

[0009] Furthermore, the output power of the auxiliary laser head is 900–1200 W.

[0010] Furthermore, the angle β between the centerline of the auxiliary laser head and the normal line of the substrate surface is 30° to 40°.

[0011] Furthermore, the first light spot is a rectangular, rounded rectangular, or near-rectangular light spot.

[0012] This invention improves the surface quality, density, and forming stability of the deposited layer by setting a first light spot that expands along the deposition path and coordinating it with the oscillation deposition process in a partitioned dwell and triggered jump manner. Attached Figure Description

[0013] Figure 1 This is a schematic diagram showing the tilt angle between the first and second light spots of the present invention; Figure 2 This is a displacement change diagram of the deposition process of the first and second light spots in one embodiment of the present invention; Figure 3 This is a displacement change diagram of the deposition process of the first and second light spots in another embodiment of the present invention; Figure 4This invention describes the cross-sectional morphology of the deposition layer of the sample obtained in the experiment, with and without the assistance of a first light spot. Figure 5 This invention provides experimental data on the high-frequency tensile strength of samples with and without the assistance of a first light spot. Figure 6 This invention describes the experimental results of the fracture morphology of the sample with and without the assistance of a first light spot. Detailed Implementation

[0014] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and embodiments. The embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them, and the scope of protection of the present invention is not limited to the following embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0015] This invention proposes a laser-assisted beam oscillation directional energy deposition manufacturing method, comprising: An auxiliary laser head is tilted to output the first light spot to form the current processing area. The current processing area is divided into a first region, a second region and a third region along the deposition direction, and the energy density decreases from the first region to the third region. The main laser head outputs a second spot and controls the second spot to scan within the current processing area according to a preset swing trajectory to achieve deposition; wherein, the first spot is a strip with a long side and a short side, the long side is arranged along the deposition direction, and the short side covers the swing trajectory envelope of the second spot; When the main laser head moves to the preset trigger position, the first laser spot is controlled to jump to the next processing zone along the deposition direction.

[0016] Specifically, the first light spot is rectangular, rounded rectangular, or near-rectangular. Compared to the conventional elliptical auxiliary light spot in existing technologies, the first light spot is elongated, which is geometrically more compatible with the elongated deposition path formed during laser directional energy deposition, facilitating the formation of a continuous thermal field coverage area in the deposition direction. The rounded rectangular light spot avoids energy concentration at sharp corners, resulting in a more uniform thermal field distribution.

[0017] Specifically, the main laser head outputs a high-energy-density second spot, which is preferably a circular spot with a diameter of 0.8–1.5 mm, preferably 1.0–1.2 mm; the main laser power is 1000–3000 W. The main laser performs periodic scanning according to a preset trajectory, which is preferably a circular, elliptical, or other periodic trajectory, with a swing amplitude preferably 0.5–2.0 mm and a swing frequency preferably 10–200 Hz.

[0018] Specifically, such as Figure 1 As shown, the centerline of the oscillating main laser processing head forms an angle α with the normal line of the substrate surface, preferably -3° to 8°. The first laser spot is incident on the substrate surface at a deflection angle. The centerline of the auxiliary laser processing head forms an angle β with the normal line of the substrate surface. Specifically, by controlling the angle of the auxiliary laser head's tilt, the energy density of the first laser spot decreases sequentially along the deposition direction. It should be noted that there is a calculable geometric relationship between the projected area of ​​the first laser spot on the workpiece surface and the average incident power density of the auxiliary laser head, but its corresponding effective absorbed energy density and actual thermal intensity are also affected by the material absorptivity, surface condition, temperature, and molten pool heat accumulation. In this invention, the specific intensity of the auxiliary thermal field formed by the first laser spot is determined by a combination of theoretical calculation and experimental calibration. For example, the energy distribution of the first laser spot along its long side can be made into a stepped shape by using diffractive optical elements or special reflectors, and the surface temperature distribution of the laser spot irradiation area can be measured by a thermal imager to confirm that the boundaries of the three regions are consistent with the set ratio; the effects of remelting, reheating, and preheating are verified through deposition experiments. These methods are existing technologies that can be implemented in this field, and will not be described in detail here.

[0019] Let the length and width of the auxiliary laser's intrinsic rectangular spot be respectively... and Then, the projected length and projected area on the workpiece surface can be approximately expressed as:

[0020] If the power of the auxiliary laser is Then its average incident power density is approximately:

[0021] Therefore, it can be seen that with The reduction in the beam size decreases the projected area of ​​the first beam spot on the workpiece surface, and increases the average incident energy density per unit area, which is more conducive to enhancing the central heating and trailing edge remelting effects; with the reduction in the beam size, the projected area of ​​the first beam spot on the workpiece surface decreases, and the average incident energy density per unit area increases, which is more conducive to enhancing the central heating and trailing edge remelting effects; The increase in angle increases the projected length of the first light spot along the deposition direction, reduces the average energy density per unit area, and is more conducive to expanding the effective range of edge preheating and continuous reheating. Therefore, The angle is preferably 30° to 40°, more preferably, The angle is 35°. The auxiliary laser power is preferably 900-1200 W, and more preferably 1000 W or 1100 W.

[0022] The length of the first light spot is set along the deposition path, and its width covers the envelope of the oscillation trajectory and the heating range on both sides. Specifically, if the diameter of the main deposition light spot is 0.5 mm, and the total oscillation width is 0.6 mm, the envelope width of the main oscillation trajectory is approximately:

[0023] The width of the first light spot is set to be slightly larger than the envelope width of the main oscillation trajectory to ensure that the undermelted areas at the edge of the oscillation trajectory can be thermally compensated. Considering the overlap between subsequent tracks, preferably, the width of the first light spot is taken as... .

[0024] Specifically, the current processing area is divided into three regions along the deposition direction: a first region, a second region, and a third region. Due to the oblique incidence, the laser energy is unevenly distributed on the substrate surface: the energy density is highest in the near region (i.e., the first region) which is close to the laser incidence direction, and the energy density is lowest in the far region (i.e., the third region) which is far from the laser incidence direction.

[0025] Based on its energy density, this application divides the functions of the three regions as follows: The first region is the remelting zone, which has the highest temperature and is used to remelt and trim the deposited area. It can release the pores and bubbles inside the deposited area, eliminate unmelted particles, smooth the surface, and reduce microcracks. The second region is the reheating zone, which is used to reheat the cold area at the edge of the oscillation trajectory envelope area to prevent the sides of the oscillation trajectory envelope area from cooling too quickly, improve the powder melting state, and reduce unmelted particles and local incomplete melting. The third region is the preheating zone, which is used to preheat the area to be deposited, reduce the temperature difference between the substrate and the molten pool, and improve the melting stability of the powder after entering the main melting zone.

[0026] To ensure the continuous operation of the auxiliary thermal field along the long strip deposition channel, the first spot in this invention employs a dwell-plus-distance jump control method. Let the center position of the first spot in the nth processing section be:

[0027] in, Let P be the initial center position of the processing interval, and P be the interval jump step size. Since this invention focuses on the continuous arrangement of the functions of the three regions within a single pass, the interval jump step size is not determined by a simple empirical value of the total length, but rather constrained by the functional continuity of the leading-edge preheating zone, the central heat-replenishing zone, and the trailing-edge remelting zone. Preferably, the step size P is 0.5 to 0.8 times the length L of the first spot, to create a 20% to 50% thermal field overlap between adjacent processing intervals, thereby avoiding heat replenishment gaps during interval switching.

[0028] Specifically, the center trajectory of the main oscillating laser processing head can be represented as:

[0029] in, and These represent the position coordinates of the main laser head in the deposition direction and the lateral oscillation direction, respectively. The deposition scanning speed of the main laser head, For time, Let be the radius of the swing. The oscillation frequency is used. During processing, the main laser continuously melts and deposits powder; the first laser spot remains within the current processing zone, performing leading-edge preheating on the area to be deposited, central heating on both sides of the oscillation trajectory envelope, and trailing-edge remelting and trimming on the deposited surface. When the main oscillation spot reaches the preset trigger position, the first laser spot moves forward to the next processing zone and continues to perform the same preheating, heating, and remelting functions. The control method does not require the auxiliary laser spot to continuously replicate the main oscillation trajectory; instead, it only needs to jump in segments along the deposition path to achieve continuous and effective auxiliary thermal field control.

[0030] Specifically, the step size P of the first light spot jumping along the deposition direction and the length L of the first light spot along the deposition direction satisfy: L - P ≥ L3, where L3 is the length of the third region of the current processing interval along the deposition direction. Therefore, after the jump, the thermal fields of the current processing interval and the next processing interval partially overlap, and the overlapping area is at least larger than the third region (preheating region). Based on the size of the overlapping area, this application provides the following specific embodiments for illustration.

[0031] In a specific embodiment, such as Figure 2 As shown, the current processing interval is numbered N1, and its corresponding first, second, and third regions are numbered N11, N12, and N13, respectively. The length of the first region is L1, the length of the second region is L2, and the length of the third region is L3, satisfying L = L1 + L2 + L3.

[0032] In this embodiment, the main laser power is 700W, and the scanning speed V = 10mm / s. The auxiliary laser head has a power of 450W. The angle is set to 35°, L to 7mm, and W to 1.3mm. The ratio of L1:L2:L3 is 2:3:2. The area of ​​the second region is slightly larger than that of the first and third regions, making the central heating zone slightly larger than the leading-edge preheating zone and the trailing-edge remelting zone, thus more fully covering the envelope of the oscillating main beam trajectory and its thermal compensation range on both sides.

[0033] In this embodiment, the preset trigger position is located in the second region N12 of the current processing zone. When the main laser head moves to the preset trigger position, the first light spot is controlled to move along the deposition direction, so that the front end of the first light spot along the deposition direction and the main laser head arrive at the starting point of the third region N13 of the current processing zone at the same time.

[0034] The specific deposition process is as follows: Initially, the second spot begins to deposit by oscillating at a scanning speed of 10 mm / s starting from P1, while the first spot remains stationary.

[0035] From 0 to 0.2 seconds, the second spot is deposited in the first region N11 (i.e., the preheating zone of the previous processing section). At this time, the first region N11 remelts the deposited sample to eliminate defects such as pores and unmelted particles. This stage utilizes the high-energy heat of region N11 to achieve immediate remelting and finishing after deposition, effectively suppressing defect formation. The second region N12 and the third region N13 work simultaneously to preheat the powder in front.

[0036] Between 0.2 and 0.4 seconds, the second spot enters the second region N12 (heating zone) for deposition. The first spot remains stationary, and all three regions continue to operate simultaneously. Specifically, the third region N13 preheats the preceding powder, the second region N12 provides heat compensation for the second spot to ensure complete powder melting, and the first region N11 continues to remelt and refine the already deposited areas. This stage, through heat compensation in the heating zone, solves the problem of insufficient powder melting caused by insufficient local dwell time under high-frequency oscillation conditions.

[0037] At 0.4–0.5 s, when the second spot moves to the preset trigger position, namely position P2, within the second region N12, the first spot is triggered to move rapidly along the deposition direction at a speed of 50 mm / s, and the second region N12 is rapidly remelted during the movement.

[0038] At 0.5s, the leading edge of the first light spot along the deposition direction (i.e., the initial boundary of the first region N11) and the second light spot simultaneously arrive at the starting point (P3 position) of the third region N13 in the current processing zone, ensuring the smoothness of the thermal field transition and avoiding local overheating or underheating caused by asynchronous jumps. At this time, the first light spot stops moving and the cycle repeats.

[0039] In the above process, the step size of the first spot jumping along the deposition direction is 5mm, which is less than the length of the first spot (7mm), satisfying LP=2mm, which is equal to the length of the third region N13. Therefore, after the jump, the first region N21 of the next processing zone N2 completely overlaps with the third region N13 of the processing zone N1, achieving the coverage of the preheating zone by the remelting zone. This allows the preheating zone to be reheated by the remelting zone after completing its preheating function, further improving the surface quality of this region.

[0040] In another specific embodiment, such as Figure 3 As shown, the current processing interval is numbered N1, and its corresponding first, second, and third regions are numbered N11, N12, and N13, respectively. The length ratio of the first, second, and third regions along the deposition direction is 1:1:1. This ratio results in a more balanced function for the three regions, smaller step sizes, and more complete overlap, making it suitable for applications with higher surface quality requirements.

[0041] In this embodiment, the main laser power is 700W, and the scanning speed V = 10mm / s. The auxiliary laser power is 400W. The angle is 35° and the length L is 6mm.

[0042] Specifically, the preset trigger position is located in the second region of the current processing zone. When the main laser head moves to the preset trigger position, the first spot is controlled to jump along the deposition direction, so that when the main laser head reaches the starting point of the third region of the current processing zone, the front end of the first spot along the deposition direction simultaneously reaches the starting point of the second region of the current processing zone.

[0043] The specific deposition process is as follows: In a certain processing cycle, the second spot moves from P1 to deposit at a scanning speed of 10 mm / s, while the first spot remains stationary. The first region N11 remelts the area where the second spot has been deposited, the second region N12 performs heat replenishment, and the third region N13 performs preheating.

[0044] For example, between 0.6 and 0.8 seconds, when the second light spot reaches the preset trigger position P2 in processing zone N1, it triggers the first light spot to move rapidly along the deposition direction. At 0.8 seconds, the leading edge of the first light spot along the deposition direction reaches position P1, and the second light spot reaches position P3. At this time, the first light spot forms processing zone N2, where the first region N21 of processing zone N2 overlaps with the second region N12, and the second region N22 of processing zone N2 overlaps with the third region N13. Then, the cycle repeats.

[0045] The main laser has deposited in the second region N12, and during the deposition process, it continuously received supplemental heating within the second region N12 to prevent excessively rapid cooling on both sides of the swing envelope. However, the deposited layer in the second region N12 may contain defects such as pores, unmelted particles, or microcracks. Since the first region N21 has the highest energy density, after the jump, the second region N12 (supplemental heating zone) of processing interval N1 overlaps with the first region N21 (remelting zone) of processing interval N2, allowing the supplemental heating zone of N1 to undergo further remelting after completing its supplemental heating function. Through high-energy remelting in subsequent intervals, the microstructure of this region is further optimized, pores are released, and unmelted particles are eliminated, thereby significantly improving the density and bonding quality of this region.

[0046] Because the third region N13 (preheating zone) of processing zone N1 overlaps with the second region N22 (reheating zone) of processing zone N2, the main laser head is just about to enter region N13 for deposition. During the deposition process, this region is simultaneously subjected to the preheating effect from the preheating zone of processing zone N1 and the real-time reheating effect from the reheating zone of processing zone N2. Therefore, the deposition by the main laser always occurs in a region that is both preheated and continuously reheated. Compared with the conventional method of remelting or reheating after deposition in the prior art, this application continuously provides heat input during the deposition process, reducing the temperature gradient between the molten pool and the surrounding area, and effectively improving the fusion quality of the envelope edge.

[0047] like Figure 4 As shown, (a) is the cross-sectional morphology of the deposited layer of the conventional oscillating sample without the assistance of the first light spot, and (b) is the cross-sectional morphology of the deposited layer of the composite manufacturing sample with the assistance of the first light spot. The comparison of cross-sectional morphologies reveals that the conventional oscillating sample exhibits significant porosity defects and unmelted particles on its surface, while the composite manufacturing sample has a denser cross-section with no obvious large pores. This indicates that the technology of this invention can effectively promote gas escape from the molten pool, reduce bubble residue and porosity formation, and improve the density and forming quality of the deposited layer. Figure 5 As shown, (a) represents the high-frequency tensile data of the conventional oscillating sample without the assistance of the first light spot, and (b) represents the high-frequency tensile data of the composite-manufactured sample with the assistance of the first light spot. The high-frequency tensile data indicate that the composite-manufactured sample has a more uniform mass, while the conventional oscillating sample is unstable under normal circular oscillation during high-frequency tensile testing.

[0048] As shown in Figure 6, (a1) to (a3) ​​represent the fracture morphology of the conventional oscillating sample without the assistance of the first light spot, while (b1) to (b3) represent the fracture morphology of the composite-manufactured sample with the assistance of the first light spot. Combining the fracture morphology, it can be seen that in addition to cracks, the conventional oscillating sample also exhibits features such as unmelted particles, pits, and cleavage steps, indicating localized insufficient melting and defect concentration, which easily become sources of crack initiation and propagation. In contrast, the composite-manufactured sample shows more pronounced dimples and tear ridges in its fracture surface, with a significant reduction in unmelted particles and pits. This demonstrates that the technology of this invention can effectively improve the powder melting state and the integrity of the deposited layer, reducing the adverse effects of defects on fracture behavior, thereby improving the overall quality and reliability of the deposited layer.

[0049] The term "an embodiment" or "embodiment" as used in this invention refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. In the description of this invention, it should be understood that the terms "first," "second," and "third," etc., in the specification, claims, and accompanying drawings are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0050] This specification provides method operation steps as shown in the embodiments or flowcharts, but based on conventional or non-inventive labor, more or fewer operation steps may be included. The order of steps listed in the embodiments is merely one of many possible execution orders and does not represent the only possible execution order. In actual system or server product execution, the method can be executed in the order shown in the embodiments or drawings, or in parallel (e.g., in a parallel processor or multi-threaded processing environment), or the execution order of steps without timing constraints can be adjusted.

[0051] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A laser-assisted beam oscillation directional energy deposition manufacturing method, characterized in that, include: An auxiliary laser head is tilted to output a first light spot to form the current processing area. The current processing area is divided into a first region, a second region, and a third region along the deposition direction, and the energy density decreases sequentially from the first region to the third region. The main laser head outputs a second spot, and controls the second spot to scan within the current processing area according to a preset swing trajectory to achieve deposition; wherein, the first spot is a strip with a long side and a short side, the long side is arranged along the deposition direction, and the short side covers the swing trajectory envelope of the second spot; When the main laser head moves to the preset trigger position, it controls the first laser spot to jump to the next processing zone along the deposition direction.

2. The method according to claim 1, characterized in that, The step size P of the first spot jumping along the deposition direction and the length L of the first spot along the deposition direction satisfy: L - P ≥ L3, where L3 is the length of the third region of the current processing interval along the deposition direction.

3. The method according to claim 2, characterized in that, The preset trigger position is located in the second region of the current processing zone. When the main laser head moves to the preset trigger position, the first light spot is controlled to move along the deposition direction, so that the front end of the first light spot along the deposition direction and the main laser head arrive at the starting point of the third region of the current processing zone at the same time.

4. The method according to claim 3, characterized in that, The length ratio of the first, second, and third regions along the depositional direction is 2:3:

2.

5. The method according to claim 2, characterized in that, The preset trigger position is located in the second region of the current processing zone. When the main laser head moves to the preset trigger position, the first spot is controlled to jump along the deposition direction, so that when the main laser head reaches the starting point of the third region of the current processing zone, the front end of the first spot along the deposition direction simultaneously reaches the starting point of the second region of the current processing zone.

6. The method according to claim 5, characterized in that, The length ratio of the first, second, and third regions along the depositional direction is 1:1:

1.

7. The method according to claim 1, characterized in that, The output power of the auxiliary laser head is 900-1200W.

8. The method according to claim 1, characterized in that, The angle β between the centerline of the auxiliary laser head and the normal line of the substrate surface is 30° to 40°.

9. The method according to claim 1, characterized in that, The first light spot is a rectangular, rounded rectangular, or near-rectangular light spot.

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