Dual-wavelength beam laser composite additive manufacturing device and method

Abstract

The invention provides a dual-wavelength beam laser composite additive manufacturing device which comprises a powder feeding nozzle, a red light laser, a green light laser and a scanning galvanometer. A red laser beam emitted by the red laser is output by the laser output channel and is focused on the processing surface to form a red light spot; a green laser beam emitted by the green laser is controlled by the scanning galvanometer to enter the red laser beam in a circular swinging mode and is focused on the machining face to form a green light spot, and the formed green light spot is located on the inner side of the red light spot. The invention provides a dual-wavelength beam laser composite additive manufacturing method. A scanning galvanometer is adopted to control a green laser beam to periodically swing in a red light spot coverage area according to a set circular path. According to the method, the dynamics and microstructure of the molten pool are optimized, the thermal gradient and the cooling rate are adjusted, and ideal conditions are provided for high-density manufacturing of materials such as nickel-based high-temperature alloy, aluminum alloy and copper alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of laser directional energy deposition, and in particular to a dual-wavelength beam laser composite additive manufacturing device and method. Background Art

[0002] Laser Directed Energy Deposition (LDED), an emerging additive manufacturing technology, holds great market application prospects in aerospace, energy, nuclear power, and other fields. Conventional LDED utilizes an infrared laser with a wavelength of 1064 nm. When depositing metals with large differences in absorptivity, such as titanium (0.65) and aluminum (0.05), the high reflectivity of aluminum leads to inefficient energy transfer to the titanium substrate and poor bonding at the aluminum / titanium interface. Furthermore, the LDED process produces directionally solidified columnar crystals, which degrade mechanical properties. Third, metallurgical defects such as pores, cracks, and incomplete fusion caused by molten pool splashing inevitably occur during the manufacturing process, resulting in reduced density of the formed part. Existing oscillating laser technology can improve metallurgical defects and regulate microstructure and mechanical properties to a certain extent, but it still cannot overcome challenges such as complex paths leading to macroscopic surface "edge waves" and low powder-laser beam coupling accuracy, which results in powder waste. Summary of the Invention

[0003] In order to solve the technical problems existing in the background technology, the present invention proposes a dual-wavelength beam laser composite additive manufacturing device and method.

[0004] The present invention proposes a dual-wavelength laser composite additive manufacturing device, comprising: a powder feeding nozzle, a red laser, a green laser, and a scanning galvanometer;

[0005] The powder feeding nozzle has a laser output channel;

[0006] The red laser is used to emit a red laser beam, and the red laser beam emitted by the red laser is output from the laser output channel of the powder feeding nozzle and focused on the processing surface to form a red light spot;

[0007] The green laser is used to emit a green laser beam, and the green laser beam emitted by it is controlled by a scanning galvanometer to enter the red laser beam in a circular swinging manner so as to be output from the laser output channel together with the red laser beam, and is focused on the processing surface to form a green light spot. The diameter of the green light spot formed is smaller than the diameter of the red light spot, and the green light spot formed is located on the inner side of the red light spot.

[0008] Preferably, the scanning galvanometer includes an X-axis galvanometer, a Y-axis galvanometer, a galvanometer motor 1 for driving the deflection of the X-axis galvanometer, and a galvanometer motor 2 for driving the deflection of the Y-axis galvanometer.

[0009] Preferably, the control conditions of the scanning galvanometer are:

[0010]

[0011] Wherein: A is the swing amplitude; F is the swing frequency; T is the time; X(t), Y(t) are the deflection angle signals of the X-axis galvanometer and the Y-axis galvanometer at time t respectively.

[0012] Preferably, the swing frequency is 0-200Hz; the swing diameter is 0-2mm.

[0013] Preferably, the power of the red laser is 500-2000W, the red light wavelength is 1064nm, and the red light spot diameter is 1-3mm.

[0014] Preferably, the power of the green laser is 50-200W, the green light wavelength is 532nm, the green light spot diameter is 1-2mm, and is smaller than the red light spot diameter.

[0015] Preferably, the powder feeding nozzle further has a powder feeding channel located at the periphery of the laser beam output channel, a cooling medium flow channel located at the periphery of the powder feeding channel, and a cooling water inlet communicating with the cooling medium flow channel.

[0016] The application provides a dual-wavelength laser beam laser composite additive manufacturing method, which comprises the following steps:

[0017] S1, a red laser emits a red laser beam, and the emitted red laser beam is emitted through the laser output channel of the powder feeding nozzle and focused on a machining surface; a green laser emits a green laser beam, and the emitted green laser beam is emitted through the scanning galvanometer, enters the red laser beam, and is output from the laser output channel of the powder feeding nozzle together with the red laser beam, and is focused on the machining surface;

[0018] S2, the scanning galvanometer controls the green laser beam to periodically swing in a circular path set in the red light spot coverage area.

[0019] In the application, the red light is directly deposited to be used for depositing main energy input, to realize overall heating, preheating and melting of metal powder and ensure deposition continuity; the green light is shot into the red light in a circular swing mode, to implement circular swing scanning with high energy density and act on a center area of a molten pool, so that columnar dendrites of the molten pool are remelted and broken by flow melt caused by the swing beam when a swing heat source is applied in a vertical direction perpendicular to a deposition direction, to improve micro-morphology and enhance mechanical properties. The combination of the two kinds of lasers generates a controllable temperature gradient, to ensure the formation of uniform equiaxed crystals. Therefore, the synergistic effect of the red light and the green light not only optimizes molten pool dynamics and micro-morphology, but also effectively adjusts a thermal gradient and a cooling rate, to provide ideal conditions for high-density manufacturing of nickel-based superalloys, aluminum alloys, copper alloys and other materials. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A structure schematic diagram of a dual-wavelength beam laser composite additive manufacturing device is provided for the present application;

[0021] Figure 2 A swing path schematic diagram of the green light beam emitted by the green light laser in the dual-wavelength beam laser composite additive manufacturing device and method provided for the present application;

[0022] Figure 3 The macroscopic and microscopic of the upper, middle and lower three layers of the cross section of the two samples of sample 1 and sample 2 are compared. DETAILED DESCRIPTION

[0023] Reference Figure 1-2 The dual-wavelength beam laser composite additive manufacturing device provided by the present application comprises a powder feeding nozzle, a red light laser 1, a green light laser 6, and a scanning galvanometer.

[0024] The powder feeding nozzle has a laser output channel located at the center position, a powder feeding channel 5 located at the periphery of the laser beam output channel, a cooling medium flow channel located at the periphery of the powder feeding channel 5, and a cooling water inlet 4 communicating with the cooling medium flow channel, wherein: the laser output channel is used for the laser beam to be emitted, the powder feeding channel 5 is used for the metal powder to be emitted to form a powder beam 9, and the cooling water inlet 4 is used for the cooling medium to be fed into the cooling flow channel.

[0025] The red light laser 1 is used for emitting a red light laser beam 2, which is output by the laser output channel and focused on the processing surface to form a red light spot.

[0026] The green light laser 6 is used for emitting a green light laser beam 7, and during processing, the green light laser beam 7 emitted thereby is incident into the red light laser beam 2 via the scanning galvanometer and is output together with the red light laser beam 2 from the laser output channel of the powder feeding nozzle, and is focused on the processing surface to form a green light spot, and the diameter of the green light spot formed is smaller than that of the red light spot.

[0027] The scanning galvanometer is used for controlling the green light laser beam 7 to periodically swing in a set circular path 11 within the red light spot coverage area 10, so that the green light spot formed by focusing the green light laser beam 7 on the processing surface is always inside the red light spot, so as to act on the molten pool, that is, in the scanning path design, the green light circular swing is superimposed on the main scanning track, so that the deposition path is a straight line or other specific route, and the green light laser makes circular disturbance at each position on the path (similar to point scanning + local stirring). The action mechanism of the swinging green light laser on the molten pool is as follows:

[0028] 1. Thermal disturbance effect: periodic local heating breaks the symmetry of temperature gradient, so that convection vortex appears in the molten pool;

[0029] 2. Fluid stirring mechanism: the laser scanning generates surface tension gradient (Marangoni effect), enhances the convection of the molten pool metal liquid, breaks the dendrites and re-nucleates in different areas;

[0030] 3. Columnar crystal breaking and nucleation: due to the continuous remelting-solidification cycle, the columnar crystals originally grown along the deposition direction are broken into small particles to form heterogeneous nucleation points, and finally promote the growth of equiaxed crystals.

[0031] The specific structure of the scanning galvanometer is as follows: the scanning galvanometer comprises an X-axis galvanometer 8, a Y-axis galvanometer 3, a galvanometer motor one for driving the X-axis galvanometer 8 to deflect, and a galvanometer motor two for driving the Y-axis galvanometer 3 to deflect. When working: the green laser 6 emits a green laser beam 7, the X-axis galvanometer 8 reflects the green laser beam 7 to the Y-axis galvanometer 3, the Y-axis galvanometer 3 reflects the green laser beam 7 to the laser output channel of the powder feeding nozzle, the X-axis galvanometer 8 is driven to deflect in the horizontal direction by the galvanometer motor one to control the deflection of the green laser beam 7 in the horizontal direction, and the Y-axis galvanometer 3 is driven to deflect in the vertical direction by the galvanometer motor two to control the deflection of the green laser beam 7 in the vertical direction, so that the green laser beam 7 draws a circular or circular-like trajectory line on the XY plane at a constant angular velocity, and presents a spiral form along the deposition direction to enhance the stirring effect. Specifically: the control condition of the scanning galvanometer (i.e. the input signal of the scanning galvanometer for controlling the green laser beam 7 to swing according to the set circular path) is as follows:

[0032]

[0033] Wherein: A is the swing amplitude (radius); f is the swing frequency; t is the time; X(t) and Y(t) are respectively the deflection angle signals of the X-axis galvanometer 8 and the Y-axis galvanometer 3 at time t. The frequency and amplitude of the circular swing are adjustable, and the specific parameters are as follows:

[0034] Swing frequency: 0-200Hz;

[0035] Swing diameter: 0-2mm.

[0036] Specifically: the power of the red laser 1 is 500-2000W, the red wavelength is 1064nm, and the red spot diameter is 1-3mm. The power of the green laser 6 is 50-200W, the green wavelength is 532nm, and the green spot diameter is 1-2mm, which is smaller than the red spot diameter.

[0037] As shown in Figure 2 The present application provides a kind of dual-wavelength beam laser composite additive manufacturing method, comprising the following steps:

[0038] S1, the red laser 1 emits a red laser beam 2, which is emitted through the laser output channel of the powder feeding nozzle and focused on the processing surface; the green laser 6 emits a green laser beam 7, which is emitted into the red laser beam 2 through the scanning galvanometer and is output from the laser output channel of the powder feeding nozzle together with the red laser beam 2, and focused on the processing surface;

[0039] S2 , the scanning galvanometer controls the green laser beam 7 to periodically oscillate along the set circular path 11 within the red light spot coverage area 10 .

[0040] Reference Figure 3 The working principle of the present invention is as follows: the red laser has a lower power density and a larger spot size, which is used for preheating, annealing and melting all powders. By preheating the substrate or the previously deposited layer, the temperature gradient in the molten pool is reduced, uniform heat distribution is promoted, and the generation of residual stress is suppressed. At the same time, the uniform heating conditions reduce the cooling rate, minimizing the directional solidification epitaxial growth of grains caused by rapid cooling. In contrast, the green laser has a higher power density and a smaller spot size, which can provide concentrated energy, use circular oscillation to stir the molten pool, and promote material deposition. At the same time, the high energy density of the green laser generates local high temperature in the molten pool, deepens and expands the molten pool, and promotes uniform material fusion.

[0041] During the solidification process, thermal gradient and cooling rate play a vital role in crystal growth. The preheating effect of the red laser 1 ensures a lower cooling rate, prevents large internal temperature differences that may cause residual stress, and promotes more uniform crystal growth. In addition, the metal powder can be captured and melted by the red light, avoiding unmelted powder on the metal surface. On the other hand, the green laser stirs the molten pool through circular swinging, and when an oscillating heat source perpendicular to the deposition direction is applied in the vertical direction, the columnar dendrites of the molten pool are re-melted and broken by the flowing melt triggered by the oscillating beam. The broken dendrites act as heterogeneous nucleation points, increasing the number of nucleations during the solidification process, destroying the continuous growth of the grains, promoting the transformation of columnar crystals to equiaxed crystals, improving the micromorphology and enhancing the mechanical properties.

[0042] Specifically: The effect of mechanical properties improvement caused by changes in microstructure is shown in Table 1 below:

[0043]

[0044] In Table 1, sample 1 was obtained by using LDED (Laser-Directed Energy Deposition) technology; sample 2 was obtained by using a dual-wavelength beam laser composite additive manufacturing device and method proposed in the present invention.

[0045] As can be seen from Table 1, the ultimate tensile strength of sample 2 obtained by using the dual-wavelength beam laser composite additive manufacturing device and method proposed in the present invention is increased by 23.13%, the elongation is increased by 97.86%, and the microhardness is increased by 7.91% compared with sample 1 obtained by LDED technology.

[0046] In summary, the dual-beam composite deposition manufacturing device and method proposed in this invention utilizes direct red light deposition and circular oscillation of green light, thereby reducing temperature gradients and slowing cooling rates. Furthermore, the molten pool disturbance caused by the green light hinders the long, thick columnar crystals extending upward from the substrate during LDED, breaking them into equiaxed crystals, significantly promoting the transformation of columnar crystals into equiaxed crystals.

[0047] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A dual-wavelength laser composite additive manufacturing device, characterized in that: include: A powder feeding nozzle, a red laser (1), a green laser (6), and a scanning galvanometer; The powder feeding nozzle has a laser output channel; The red laser (1) is used to emit a red laser beam (2), and the emitted red laser beam (2) is output from a laser output channel of a powder feeding nozzle and focused on a processing surface to form a red light spot; The green laser (6) is used to emit a green laser beam (7), and the emitted green laser beam (7) is controlled by a scanning galvanometer to be injected into the red laser beam (2) in a circular swinging manner so as to be output together with the red laser beam (2) from the laser output channel of the powder feeding nozzle and focused on the processing surface to form a green light spot, wherein the diameter of the formed green light spot is smaller than the diameter of the red light spot, and the formed green light spot is located inside the red light spot.

2. The dual-wavelength laser composite additive manufacturing device according to claim 1, characterized in that: The scanning galvanometer comprises an X-axis galvanometer (8), a Y-axis galvanometer (3), a galvanometer motor 1 for driving the X-axis galvanometer (8) to deflect, and a galvanometer motor 2 for driving the Y-axis galvanometer (3) to deflect.

3. The dual-wavelength laser composite additive manufacturing device according to claim 2, characterized in that: The control conditions of the scanning galvanometer are: Wherein: A is the swing amplitude; f is the swing frequency; t is time; X(t) and Y(t) are the deflection angle signals of the X-axis galvanometer (8) and the Y-axis galvanometer (3) at time t respectively.

4. The dual-wavelength laser composite additive manufacturing device according to claim 3, characterized in that: The swing frequency is: 0-200Hz; the swing diameter is: 0-2mm.

5. The dual-wavelength laser composite additive manufacturing device according to claim 1, characterized in that: The power of the red laser (1) is 500-2000W, the wavelength of the red light is 1064nm, and the diameter of the red light spot is 1-3mm.

6. The dual-wavelength laser composite additive manufacturing device according to claim 1, characterized in that: The power of the green laser (6) is 50-200W, the wavelength of the green light is 532nm, and the diameter of the green light spot is 1-2mm, which is smaller than the diameter of the red light spot.

7. The dual-wavelength laser composite additive manufacturing device according to claim 1, characterized in that: The powder feeding nozzle also comprises a powder feeding channel (5) located on the periphery of the laser beam output channel, a cooling medium flow channel located on the periphery of the powder feeding channel (5), and a cooling water inlet (4) connected to the cooling medium flow channel.

8. A dual-wavelength laser composite additive manufacturing method, characterized in that: The following steps are involved: S1, a red laser (1) emits a red laser beam (2), and the emitted red laser beam (2) is emitted through the laser output channel of the powder feeding nozzle and focused on the processing surface; a green laser (6) emits a green laser beam (7), and the emitted green laser beam (7) is injected into the red laser beam (2) through the scanning galvanometer and emitted together with the red laser beam (2) from the laser output channel of the powder feeding nozzle and focused on the processing surface; S2. The scanning galvanometer controls the green laser beam (7) to periodically oscillate along a set circular path (11) within the red light spot coverage area (10).

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