High energy utilization laser additive manufacturing method and system

Abstract

The application belongs to the technical field of laser additive manufacturing, and discloses a high-energy-utilization laser additive manufacturing method and system. The method is suitable for laser powder bed melting and directional energy deposition processes, and comprises the following steps: promoting the formation of a first stable keyhole in the molten pool of the current deposition layer on the forming platform by adjusting the energy density / power distribution / wavelength range of the main laser, introducing an auxiliary heat source or / and changing the printing environment within a period of time; monitoring the state of the keyhole in the molten pool in real time, dynamically adjusting the main laser, the auxiliary heat source or / and the printing environment based on the monitored keyhole state information, so as to switch to and maintain a second stable keyhole, which is the same as or different from the first stable keyhole and can be switched between different stable keyholes according to manufacturing requirements; and completing the additive manufacturing process through layer-by-layer deposition. The application can effectively improve the laser energy utilization, reduce the economic cost and improve the forming quality.

Description

Technical Field

[0001] This invention relates to the field of laser additive manufacturing technology, and in particular to a laser additive manufacturing method and system with high energy utilization. Background Technology

[0002] Additive manufacturing (also known as 3D printing) offers high design and forming freedom, making it suitable for manufacturing multi-scale, multi-material, and multi-functional components. Its on-site, on-demand manufacturing capabilities significantly enhance social and economic resilience. Laser additive manufacturing uses lasers as a heat source to melt and fuse material units such as powder particles and filaments, and has been applied in aerospace, defense, energy, and biomedicine. Generally, laser additive manufacturing mainly includes two technologies: laser powder bed melting (also known as selective laser melting or selective laser sintering) and laser directional energy deposition (also known as laser cladding or laser near-net-shape forming). Regarding laser selection, both technologies commonly use mature and cost-effective (near)infrared lasers (typically with a wavelength of around 1 μm). However, they generally suffer from low laser energy utilization, especially when using high-reflectivity materials such as aluminum and aluminum alloys, copper and copper alloys, silver and silver alloys, and gold and gold alloys as raw materials. For example, pure copper typically absorbs only about 5% of the energy of near-infrared lasers with a wavelength of approximately 1 μm. Low energy efficiency leads to energy waste, and unabsorbed laser light reflected back to optical components may damage the optical components or the laser additive manufacturing system.

[0003] To address the aforementioned issues, existing laser additive manufacturing technologies primarily consider using blue and green lasers as heat sources. By employing shorter wavelength lasers, the absorption rate of high-reflectivity materials such as copper and copper alloys, gold and gold alloys, to laser energy is increased. However, this strategy currently has limitations: (1) Although using short-wavelength lasers improves utilization, its energy utilization rate has not yet reached an ideal level and there is still room for improvement; (2) Blue and green lasers have low technological maturity, and their economic cost is often several times that of (near)infrared lasers, while their lifespan is only a fraction of that of (near)infrared lasers; (3) Due to the Rayleigh scattering effect, blue and green lasers are more easily scattered by tiny particles (such as submicron-sized powder particles or sputtering particles) in the forming cavity, causing optical path attenuation, thereby reducing the stability of the forming process and leading to a decrease in forming quality; (4) The significant thermal absorption effect of blue and green lasers results in a low power limit for blue and green lasers, making it difficult to achieve high-power, high-speed printing. Increasing the number of lasers to improve energy density would further increase economic costs. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, one objective of this invention is to provide a high-energy-efficiency laser additive manufacturing method and system, which can effectively improve laser energy utilization, reduce economic costs, and improve forming quality.

[0005] The high-energy-efficiency laser additive manufacturing method provided by the first aspect of the present invention is applicable to laser powder bed melting and directional energy deposition processes, and includes the following steps:

[0006] S1: By adjusting the energy density / power distribution / wavelength range of the main laser over a period of time, introducing an auxiliary heat source, and / or changing the printing environment, the formation of a first steady-state keyhole is promoted in the molten pool of the current deposited layer on the forming platform; the energy density refers to the amount of energy input by the main laser into a unit volume of material, the power distribution refers to the spatial or temporal distribution of the power density of the main laser, and the power density refers to the amount of power input by the main laser into a unit area of ​​material;

[0007] S2: Monitor the state of the keyhole in the molten pool in real time, and dynamically adjust the main laser, auxiliary heat source and / or printing environment based on the monitored keyhole state information to switch to and maintain a second stable keyhole. The second stable keyhole may be the same as or different from the first stable keyhole. The second stable keyhole can be switched between different stable keyholes according to manufacturing requirements.

[0008] S3: Repeat steps S1 and S2 to complete the additive manufacturing process by depositing material layer by layer.

[0009] The high-energy-efficiency laser additive manufacturing method of this invention has the following advantages:

[0010] I. Improve Energy Utilization. Regardless of the type and wavelength of the main laser, or the type and size of the material, introducing a steady-state keyhole can improve the overall energy utilization of the laser, thereby achieving high-efficiency additive manufacturing. For example... Figure 7 As shown, by introducing a steady-state keyhole, the energy absorption rate of pure copper for near-infrared laser with a wavelength of about 1 μm increased from about 5% to about 60%, and the energy absorption rate for blue laser with a wavelength of about 450 nm also increased from about 65% to about 83%.

[0011] Second, reduce economic costs. Using a conventional (near) infrared laser as the main laser, compared with short-wavelength lasers, can not only significantly reduce the economic costs of manufacturing and the system, but also effectively extend the service life of the system.

[0012] Third, improve forming quality. By introducing a steady-state keyhole, the forming process of additive manufacturing (such as material melting and fusion) can be made more stable, which can effectively improve the accuracy of additive manufacturing and reduce the defect rate, thereby helping to form high-quality complex components.

[0013] In some embodiments, in step S1, the first steady-state keyhole refers to the keyhole structure information satisfying a first preset condition and remaining stable for a period of time. The keyhole structure information includes at least one of the following: morphology, depth, width, aspect ratio, length, area, volume, front wall angle, curvature, roughness, speed, amplitude, frequency, temperature, pressure, oxygen content, distribution, gradient, elemental composition, evaporation rate, light absorption rate, and fluctuations.

[0014] In step S2, the second steady-state keyhole refers to the keyhole structure information satisfying the second preset condition and remaining stable for a period of time; the keyhole structure information includes at least one of the following: morphology, depth, width, aspect ratio, length, area, volume, front wall angle, curvature, roughness, velocity, amplitude, frequency, temperature, pressure, oxygen content, distribution, gradient, elemental composition, evaporation rate, light absorption rate, and fluctuations.

[0015] In some embodiments, in step S1, at least one of the structural features of one or more of the following corresponding to the first steady-state keyhole—molten pool, steam plume, plasma, splash, ambient atmosphere, chamber environment, and solidification structure—satisfies the corresponding preset conditions and remains stable for a period of time. The structural features include morphology, size, quantity, overlap, trajectory, surface properties, state, velocity, amplitude, frequency, temperature, pressure, composition, density, oxygen content, distribution, gradient, elemental composition, type, grain size, orientation, phase composition, precipitates, defects, subgrain structure, microstructure uniformity, residual stress, and fluctuations.

[0016] In step S2, at least one of the structural features of the molten pool, steam plume, plasma, splash, ambient atmosphere, chamber environment, and solidification structure corresponding to the second steady-state keyhole satisfies the corresponding preset conditions and remains stable for a period of time. The structural features include morphology, size, quantity, overlap, trajectory, surface properties, state, velocity, amplitude, frequency, temperature, pressure, composition, density, oxygen content, distribution, gradient, elemental composition, type, grain size, orientation, phase composition, precipitates, defects, subgrain structure, microstructure uniformity, residual stress, and fluctuations.

[0017] In some embodiments, in step S1, the adjustment method for promoting the formation of the first steady-state keyhole includes at least one of the following methods, or any combination of the following methods: adjusting the output power of the main laser, adjusting the scanning rate of the main laser, adjusting the power distribution characteristics of the main laser, adjusting the swing path of the main laser, adjusting the incident angle and polarization of the main laser, using a wavelength-tunable main laser, introducing an auxiliary heat source, and changing the printing environment; and the promotion process is divided into a first stage and a second stage for forming the first steady-state keyhole.

[0018] The adjustment of the output power of the main laser includes: in the first stage, the main laser uses a larger output power, and in the second stage, the main laser gradually reduces the output power to a suitable value;

[0019] Adjusting the scanning rate of the main laser includes: using a lower scanning rate for the main laser in the first stage, and gradually increasing the scanning rate of the main laser to a suitable value in the second stage;

[0020] Adjusting the power distribution characteristics of the main laser includes: in the first stage, the main laser uses a beam distribution with high energy concentration; in the second stage, the main laser gradually reduces the energy concentration of the beam distribution to a suitable value; the power distribution characteristics include the spot shape, spot size, peak power and its spatial distribution, power density distribution, pulse width, pulse frequency, pulse waveform, duty cycle, and the spatiotemporal coupled power distribution formed during the scanning process of the main laser.

[0021] Adjusting the oscillation path of the main laser includes: in a first stage, adjusting the oscillation path of the main laser to prolong the interaction time between the laser and the material, and / or to increase the energy concentration of the laser; in a second stage, adjusting the oscillation path of the main laser to gradually decrease the interaction time between the laser and the material until a suitable value is reached, and / or to gradually decrease the energy concentration of the laser until a suitable value is reached; the oscillation path includes at least one of the following: linear oscillation, sawtooth oscillation, triangular wave oscillation, stepped oscillation, broken line oscillation, sine oscillation, cosine oscillation, circular oscillation, elliptical oscillation, figure-eight oscillation, spiral oscillation, petal oscillation, random oscillation, quasi-random oscillation, adaptive oscillation, multi-frequency superposition oscillation, amplitude or frequency gradual oscillation, and asymmetric oscillation, or any combination of the above oscillation paths;

[0022] Adjusting the incident angle and polarization of the main laser includes: in the first stage, the main laser uses an incident angle / polarization that matches the high laser absorptivity, and in the second stage, the main laser gradually adjusts the incident angle / polarization to a suitable value that matches the low laser absorptivity.

[0023] The wavelength-tunable master laser includes: in a first stage, the master laser outputs a short-wavelength laser, or outputs a wavelength laser that matches a high laser absorptivity; in a second stage, the master laser gradually increases the laser wavelength to a suitable value, or gradually adjusts the laser wavelength to a suitable value that matches a low laser absorptivity.

[0024] The auxiliary heat source is introduced by: turning on the auxiliary heat source at a higher power in the first stage, and gradually reducing the power of the auxiliary heat source to a suitable value in the second stage; the auxiliary heat source is used to increase the energy input into the molten pool, and the auxiliary heat source includes at least one of coaxial laser, off-axis laser, electron beam, plasma beam, electric arc, hot lamp, hot gas heater, resistance heater, induction heater, infrared heater, microwave heater, and ultrasonic heater, or any combination of the above auxiliary heat sources;

[0025] Changing the printing environment includes: in the first stage, the printing environment uses conditions that match a high laser absorptivity, and in the second stage, the printing environment is gradually adjusted to suitable conditions that match a low laser absorptivity; the printing environment includes at least one of gas type, gas composition, gas temperature, gas flow rate, oxygen content, oxygen partial pressure, chamber pressure, chamber temperature, and material surface treatment and modification, or any combination of the printing environment;

[0026] One or more of the methods used in the first stage of forming the first steady-state keyhole are employed to increase the energy input into the molten pool for a period of time, or / and to increase the energy concentration into the molten pool for a period of time;

[0027] One or more of the methods used in the second stage of forming the first steady-state keyhole are employed to gradually reduce the energy input into the molten pool until a suitable value is reached, or / and to gradually reduce the energy concentration into the molten pool until a suitable value is reached.

[0028] In some embodiments, the second steady-state keyhole is maintained in step S2 by:

[0029] The output power of the main laser is adjusted, wherein the output power of the main laser is dynamically adjusted based on the monitored keyhole state information in order to maintain the second steady-state keyhole.

[0030] The scanning rate of the main laser is adjusted, wherein the scanning rate of the main laser is dynamically adjusted based on the monitored keyhole state information in order to maintain the second steady-state keyhole.

[0031] The power distribution characteristics of the main laser are adjusted, wherein the power distribution characteristics of the main laser are dynamically adjusted based on the monitored keyhole state information to maintain the second steady-state keyhole; the power distribution characteristics include spot shape, spot size, peak power and its spatial distribution, power density distribution, pulse width, pulse frequency, pulse waveform, duty cycle, and spatiotemporal coupled power distribution formed during the scanning process of the main laser;

[0032] The swing path of the main laser is adjusted, wherein the swing path of the main laser is dynamically adjusted based on the monitored keyhole state information to maintain the second steady-state keyhole; the swing path includes at least one of the following: linear swing, sawtooth swing, triangular wave swing, stepped swing, broken line swing, sine swing, cosine swing, circular swing, elliptical swing, figure-eight swing, spiral swing, petal swing, random swing, quasi-random swing, adaptive swing, multi-frequency superposition swing, amplitude or frequency gradual swing, and asymmetric swing, or any combination of the above swing paths;

[0033] The incident angle and polarization of the main laser are adjusted, wherein the incident angle and polarization of the main laser are dynamically adjusted based on the monitored keyhole state information in order to maintain the second steady-state keyhole.

[0034] The wavelength-tunable main laser is used, wherein the laser wavelength of the main laser is dynamically adjusted based on the monitored keyhole state information to maintain the second steady-state keyhole.

[0035] The auxiliary heat source is introduced, wherein the energy output of the auxiliary heat source is dynamically adjusted based on the monitored keyhole status information to maintain the second steady-state keyhole; the auxiliary heat source is used to adjust the energy input entering the molten pool, and the auxiliary heat source includes at least one of coaxial laser, off-axis laser, electron beam, plasma beam, electric arc, hot lamp, hot air heater, resistance heater, induction heater, infrared heater, microwave heater, and ultrasonic heater, or any combination of the above auxiliary heat sources;

[0036] Or / and, change the printing environment, wherein the printing environment is dynamically adjusted based on the monitored keyhole state information to maintain the second steady-state keyhole; the printing environment includes at least one of gas type, gas composition, gas temperature, gas flow rate, oxygen content, oxygen partial pressure, chamber pressure, chamber temperature and material surface treatment and modification, or any combination of the printing environment.

[0037] In some embodiments, the second steady-state keyhole can be switched between different steady-state keyholes according to manufacturing requirements:

[0038] At least one structural feature of the keyhole structure of the steady-state keyhole before and after the switch remains stable for a period of time before and after the switch; the structural feature includes, but is not limited to, morphology, depth, width, aspect ratio, length, area, volume, front wall angle, curvature, roughness, velocity, amplitude, frequency, temperature, pressure, oxygen content, distribution, gradient, elemental composition, evaporation rate, light absorption rate, and fluctuations.

[0039] Or / and, at least one of the structural features of the molten pool, steam plume, plasma, splash, ambient atmosphere, chamber environment, solidification structure, etc., corresponding to the keyhole structures of the steady-state keyhole before and after the switch, remain stable for a period of time before and after the switch; the structural features include, but are not limited to, morphology, size, quantity, overlap, trajectory, surface properties, state, velocity, amplitude, frequency, temperature, pressure, composition, density, oxygen content, distribution, gradient, elemental composition, type, grain size, orientation, phase composition, precipitates, defects, subgrain structure, microstructure uniformity, residual stress, and fluctuations;

[0040] The manufacturing requirements include, but are not limited to, changes or adjustments to at least one of the following: material type, morphology, size, quantity, surface properties, state, composition, density, oxygen content, distribution, gradient within the forming area, and the size, wall thickness, layer thickness, internal channels, surface properties, support, chamfer, pore structure, grid structure, gradient structure, solidification structure, mechanical properties, corrosion properties, optical properties, acoustic properties, electrical properties, magnetic properties, thermal properties, and biological properties within the forming area.

[0041] In some embodiments, an in-situ monitoring device is used to monitor keyhole status information in the molten pool. The monitoring information includes, but is not limited to, at least one of the following: optical signals, acoustic signals, electrical signals, magnetic signals, thermal signals, mechanical signals, geometric morphology signals, chemical composition signals, radiation signals, fluid flow field signals, phase and microstructure signals, and time and process characteristic signals. This information is used to dynamically adjust at least one printing parameter of the main laser, the auxiliary heat source, and / or the printing environment. The in-situ monitoring device includes, but is not limited to, an X-ray imaging device, an X-ray scattering and diffraction device, an optical coherence tomography device, a molten pool monitoring camera, and an infrared sensor. The device includes one or more of the following: camera, visible light camera, ultraviolet camera, laser interferometer, spectrometer, plasma radiation monitoring device, pyrometer, thermocouple, photodiode, acoustic monitoring device, microphone, thermionic detection device, eddy current detection device, magneto-optical imaging device, integrating sphere, oxygen content sensor, gas composition analyzer, and pressure sensor; the printing parameters include, but are not limited to, power, scanning rate, spot shape, spot size, peak power, peak distribution, pulse width, pulse frequency, pulse waveform, duty cycle, gas type, gas composition, gas temperature, gas flow rate, oxygen content, oxygen partial pressure, chamber pressure, chamber temperature, and material surface treatment and modification.

[0042] The keyhole state information includes, but is not limited to, at least one of the observation, measurement, and inference information regarding the morphology, depth, width, aspect ratio, length, area, volume, front wall angle, curvature, roughness, velocity, amplitude, frequency, temperature, pressure, oxygen content, distribution, gradient, elemental composition, evaporation rate, light absorptivity, fluctuations, and their respective changes of the keyhole structure, or / and, at least one of the observation, measurement, and inference information regarding optical signals, acoustic signals, electrical signals, magnetic signals, thermal signals, mechanical signals, geometric morphology signals, chemical composition signals, radiation signals, fluid flow field signals, phase and microstructure signals, and time and process characteristic signals generated by one or more of the structures or objects corresponding to the keyhole structure, such as molten pool, steam plume, plasma, splash, ambient atmosphere, chamber environment, and solidification structure.

[0043] In some embodiments, at least one printing parameter of the main laser, the auxiliary heat source, and / or the printing environment is dynamically adjusted based on the monitored keyhole status information; the printing parameters include power, scanning rate, spot shape, spot size, peak power, peak distribution, pulse width, pulse frequency, pulse waveform, duty cycle, gas type, gas composition, gas temperature, gas flow rate, oxygen content, oxygen partial pressure, chamber pressure, chamber temperature, and material surface treatment and modification.

[0044] In some embodiments, the high-energy-efficiency laser additive manufacturing method is applicable to single-laser additive manufacturing systems, multi-laser additive manufacturing systems, and composite high-energy-beam additive manufacturing systems with lasers as the main heat source.

[0045] A second aspect of the present invention also proposes a high-energy-efficiency laser additive manufacturing system.

[0046] The high energy efficiency laser additive manufacturing system according to the second aspect of the present invention utilizes the high energy efficiency laser additive manufacturing method according to the first aspect of the present invention.

[0047] Since the high energy efficiency laser additive manufacturing system of the second aspect embodiment of the present invention utilizes the high energy efficiency laser additive manufacturing method of the first aspect embodiment of the present invention, the high energy efficiency laser additive manufacturing system of the second aspect embodiment of the present invention has essentially the same technical effects as the high energy efficiency laser additive manufacturing method of the first aspect embodiment of the present invention, and will not be described again here.

[0048] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the laser powder bed melting system according to an embodiment of the present invention;

[0050] Figure 2 This is a schematic diagram of a laser-directed energy deposition system according to an embodiment of the present invention;

[0051] Figure 3 This is a schematic diagram showing the change of the power of the main laser over time in the high energy utilization laser additive manufacturing method of this invention.

[0052] Figure 4 This is a schematic diagram showing the change of the scanning rate of the main laser over time in the high energy utilization laser additive manufacturing method of this invention.

[0053] Figure 5 This is a schematic diagram showing the change of power of the auxiliary heat source over time in the high energy utilization laser additive manufacturing method of this invention.

[0054] Figure 6 This is a schematic diagram showing the power of another main laser changing over time in the high-energy-utilization laser additive manufacturing method of this invention.

[0055] Figure 7 This is a comparison chart of the absorption rates of pure copper for near-infrared and blue laser light under conditions of no introduction and with the introduction of a steady-state keyhole.

[0056] Figure Labels

[0057] Laser powder bed melting system 100; laser directional energy deposition system 200; main laser 1; main laser 2; first dichroic mirror 31; second dichroic mirror 32; auxiliary laser 4; auxiliary laser 5; optical signal 6; coaxial monitoring device 7; scanning galvanometer 8; focusing lens 9; off-axis auxiliary heat source 10; off-axis monitoring device 11; forming chamber 12; powder bed 13; printing component 14; forming platform 15; resistance heater 16; first lead screw 171; second lead screw 172; powder supply platform 18; powder supply chamber 19; scraper 20; powder material 21; current deposition layer 22; molten pool 23; keyhole 24; nozzle 25. Detailed Implementation

[0058] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0059] The following is combined Figures 1 to 7 This invention describes a high-energy-efficiency laser additive manufacturing method and system according to embodiments of the present invention.

[0060] like Figures 1 to 7 As shown, the high energy utilization laser additive manufacturing method of the first aspect of the present invention is applicable to laser powder bed melting (… Figure 1 ) and laser-directed energy deposition ( Figure 2 The process includes the following steps:

[0061] S1: By adjusting the energy density / power distribution / wavelength range of the main laser 2 (arrow A indicates the scanning direction of the main laser 2) over a period of time, introducing an auxiliary heat source (auxiliary laser 5 or off-axis auxiliary heat source 10 or resistance heater 16) and / or changing the printing environment, the formation of the first steady-state keyhole is promoted in the molten pool 23 of the current deposited layer on the forming platform 15; energy density refers to the amount of energy input by the main laser 2 into a unit volume of material, power distribution refers to the spatial or temporal distribution of the power density of the main laser 2, and power density refers to the amount of power input by the main laser 2 into a unit area of ​​material;

[0062] S2: The state of the keyhole 24 in the molten pool 23 is monitored in real time. Based on the monitored keyhole state information, the main laser 2, auxiliary heat source (auxiliary laser 5 or off-axis auxiliary heat source 10 or resistance heater 16) and / or printing environment are dynamically adjusted to switch to and maintain the second stable keyhole. The second stable keyhole may be the same as or different from the first stable keyhole. The second stable keyhole can be switched between different stable keyholes according to manufacturing requirements.

[0063] S3: Repeat steps S1 and S2 to complete the additive manufacturing process by depositing material layer by layer.

[0064] Introducing a steady-state keyhole into the molten pool 23 increases the number of reflections and absorptions of the main laser 2 on the local liquid material surface, and also increases the incident angle of the main laser 2 relative to the local liquid material surface, thereby improving the overall energy utilization rate of laser additive manufacturing. This is not limited to the type of main laser 1 or the wavelength of the main laser 2, nor is it limited to the type and size of the material 21. By introducing a steady-state keyhole, the overall energy utilization rate of laser additive manufacturing can be improved. For example, using this technology, a conventional (near) infrared main laser 1 can be used to achieve highly efficient additive manufacturing of components made of high-reflectivity materials such as aluminum and aluminum alloys, copper and copper alloys, silver and silver alloys, and gold and gold alloys.

[0065] The high-energy-efficiency laser additive manufacturing method of this invention has the following advantages:

[0066] I. Improving Energy Utilization. Regardless of the type of main laser 1 or the wavelength of the main laser 2, nor the type and size of material 21, the overall energy utilization of the laser can be improved by introducing a steady-state keyhole, thereby achieving high-efficiency additive manufacturing. For example... Figure 7 As shown, by introducing a steady-state keyhole, the energy absorption rate of pure copper for near-infrared laser with a wavelength of about 1 μm increased from about 5% to about 60%, and the energy absorption rate for blue laser with a wavelength of about 450 nm also increased from about 65% to about 83%.

[0067] II. Reduced Economic Costs. Using a conventional (near) infrared laser as the main laser 1, compared to short-wavelength lasers, not only significantly reduces the economic costs of manufacturing and the system, but also effectively extends the system's lifespan.

[0068] III. Improving Forming Quality. Laser additive manufacturing is a highly dynamic process, with different states of the keyhole 24 in different forming regions / stages. By switching from the first stable keyhole to the second stable keyhole, and by switching between different stable keyholes through the second stable keyhole, the forming process of additive manufacturing (such as material melting and fusion) can be made more stable, which can effectively improve the accuracy of additive manufacturing and reduce the defect rate, thereby contributing to the high-quality forming of complex components.

[0069] In some embodiments, in step S1, the first steady-state keyhole refers to the keyhole structure information satisfying the first preset condition and remaining stable for a period of time; the keyhole structure information includes, but is not limited to, at least one of morphology, depth, width, aspect ratio, length, area, volume, front wall angle, curvature, roughness, speed, amplitude, frequency, temperature, pressure, oxygen content, distribution, gradient, elemental composition, evaporation rate, light absorption rate, and fluctuations; the keyhole structure refers to the vapor depression area formed by the back pressure generated by the vaporization of local materials under laser action, which overcomes the surface tension, gravity, and other factors of the liquid material, causing the surface of the liquid material in the laser action zone in the molten pool to be depressed.

[0070] In step S2, the second steady-state keyhole refers to the keyhole structure information satisfying the second preset condition and remaining stable for a period of time; the keyhole structure information includes, but is not limited to, at least one of the following: morphology, depth, width, aspect ratio, length, area, volume, front wall angle, curvature, roughness, velocity, amplitude, frequency, temperature, pressure, oxygen content, distribution, gradient, elemental composition, evaporation rate, light absorption rate, and fluctuations.

[0071] In some embodiments, at least one of the structural features of one or more of the structures or objects corresponding to the first steady-state keyhole, such as molten pool, steam plume, plasma, splash, ambient atmosphere, chamber environment, and solidification structure, satisfies the corresponding preset conditions and remains stable for a period of time; the structural features include, but are not limited to, morphology, size, quantity, overlap, trajectory, surface properties, state, velocity, amplitude, frequency, temperature, pressure, composition, density, oxygen content, distribution, gradient, elemental composition, type, grain size, orientation, phase composition, precipitates, defects, subgrain structure, microstructure uniformity, residual stress, and fluctuations;

[0072] At least one of the structural features of the structure or object corresponding to the second steady-state keyhole, such as molten pool, steam plume, plasma, splash, ambient atmosphere, chamber environment, solidification structure, etc., satisfies the corresponding preset conditions and remains stable for a period of time; the structural features include, but are not limited to, morphology, size, quantity, overlap, trajectory, surface properties, state, velocity, amplitude, frequency, temperature, pressure, composition, density, oxygen content, distribution, gradient, elemental composition, type, grain size, orientation, phase composition, precipitates, defects, subgrain structure, microstructure uniformity, residual stress and fluctuations.

[0073] In some embodiments, in step S1, the adjustment method for promoting the formation of the first steady-state keyhole includes at least one of the following methods, or any combination of the following methods: adjusting the output power of the main laser 1, adjusting the scanning rate of the main laser 2, adjusting the power distribution characteristics of the main laser 2, adjusting the oscillation path of the main laser 2, adjusting the incident angle and polarization of the main laser 2, using a wavelength-tunable main laser 1, introducing an auxiliary heat source (auxiliary laser 5 or off-axis auxiliary heat source 10 or resistance heater 16), and changing the printing environment, etc.; and the promotion process is divided into a first stage for forming the first steady-state keyhole (see Figures 3 to 6 Phase I) and Phase II (see Figures 3 to 6 Phase II in the middle).

[0074] Adjusting the output power of the main laser 1 includes: Figure 3 and Figure 6 As shown, in the first stage, the main laser 1 uses a larger output power, and in the second stage, the main laser 1 gradually reduces the output power to a suitable value.

[0075] Adjust the scanning rate of the main laser 2, including: Figure 4 As shown, in the first stage, the main laser 2 uses a low scanning rate (which can be zero), and in the second stage, the main laser 2 gradually increases the scanning rate to a suitable value;

[0076] Adjusting the power distribution characteristics of the main laser 2 includes: using a high-energy-concentration beam distribution in the first stage, and gradually reducing the energy concentration of the beam distribution to a suitable value in the second stage; the power distribution characteristics include, but are not limited to, the spot shape, spot size, peak power and its spatial distribution, power density distribution, pulse width, pulse frequency, pulse waveform, duty cycle, and the spatiotemporal coupling power distribution formed during the scanning process of the main laser 2; the energy concentration of the beam distribution refers to the ability of a laser to concentrate energy into a very small area or a very small time in space or time, which usually means high energy density or high power density;

[0077] Adjusting the oscillation path of the main laser 2 includes: in the first stage, adjusting the oscillation path of the main laser 2 to prolong the interaction time between the laser and the material, and / or to increase the energy concentration of the laser; in the second stage, adjusting the oscillation path of the main laser 2 to gradually decrease the interaction time between the laser and the material until a suitable value is reached, and / or to gradually decrease the energy concentration of the laser until a suitable value is reached; the oscillation path includes, but is not limited to, at least one of the following: linear oscillation, sawtooth oscillation, triangular wave oscillation, stepped oscillation, broken line oscillation, sine oscillation, cosine oscillation, circular oscillation, elliptical oscillation, figure-eight oscillation, spiral oscillation, petal oscillation, random oscillation, quasi-random oscillation, adaptive oscillation, multi-frequency superposition oscillation, amplitude or frequency gradual oscillation, and asymmetric oscillation, or any combination of the above oscillation paths;

[0078] Adjusting the incident angle and polarization of the main laser 2 includes: in the first stage, the main laser 2 uses an incident angle / polarization that matches the high laser absorptivity, and in the second stage, the main laser 2 gradually adjusts the incident angle / polarization to a suitable value that matches the low laser absorptivity.

[0079] The main laser 1 with a wavelength tunable includes: in the first stage, the main laser 1 outputs a short-wavelength laser, or outputs a laser wavelength that matches a high laser absorptivity; in the second stage, the main laser 1 gradually increases the laser wavelength to a suitable value, or gradually adjusts the laser wavelength to a suitable value that matches a low laser absorptivity.

[0080] Introducing an auxiliary heat source (auxiliary laser 5 or off-axis auxiliary heat source 10 or resistance heater 16), including: such as Figure 5 As shown, in the first stage, the auxiliary heat source is turned on with a large power, and in the second stage, the power of the auxiliary heat source is gradually reduced to a suitable value (which may not be zero). The auxiliary heat source is used to increase the energy input into the molten pool, including but not limited to at least one of coaxial laser, off-axis laser, electron beam, plasma beam, electric arc, hot lamp, hot gas heater, resistance heater, induction heater, infrared heater, microwave heater, and ultrasonic heater, or any combination of the above auxiliary heat sources.

[0081] The printing environment may be modified, including: in the first stage, the printing environment is used under conditions that match the high laser absorption rate, and in the second stage, the printing environment is gradually adjusted to suitable conditions that match the low laser absorption rate; the printing environment includes, but is not limited to, at least one of the following: gas type, gas composition, gas temperature, gas flow rate, oxygen content, oxygen partial pressure, chamber pressure, chamber temperature, and material surface treatment and modification, or any combination of the above printing environments.

[0082] One or more of the methods used in the first stage of forming the first steady-state keyhole are employed to increase the energy input into the molten pool 23 for a period of time, and / or to increase the energy concentration into the molten pool 23 for a period of time; the one or more methods produce the same or equivalent effects;

[0083] One or more of the methods used in the second stage of forming the first steady-state keyhole are employed to gradually reduce the energy input into the molten pool 23 until a suitable value is reached, or / and to gradually reduce the energy concentration into the molten pool 23 until a suitable value is reached; the one or more methods produce the same or equivalent effects.

[0084] The above methods all employ a phased strategy to ensure the stable establishment of the first steady-state keyhole. Various methods can be used, such as adjusting the output power of the main laser 1, adjusting the scanning rate of the main laser 2, adjusting the power distribution characteristics of the main laser 2, adjusting the oscillation path of the main laser 2, adjusting the incident angle and polarization of the main laser 2, using a wavelength-tunable main laser 1, introducing an auxiliary heat source (auxiliary laser 5, or off-axis auxiliary heat source 10, or resistance heater 16), and changing the printing environment. These methods can be used individually or in combination to adapt to the manufacturing needs of different materials and structures at different stages, thereby achieving high energy utilization and high-quality forming of complex components.

[0085] In some embodiments, the method for maintaining the second steady-state keyhole in step S2 is as follows (see...) Figures 3 to 6 Phase III):

[0086] Adjust the output power of the main laser 1, where, for example Figure 3 and Figure 6 As shown, the output power of the main laser 1 is dynamically adjusted based on the monitored state information of the keyhole 24 to maintain the second steady-state keyhole, avoid insufficient or excessive energy input, and thus ensure the stability of the additive manufacturing process.

[0087] Adjust the scanning rate of the main laser 2, where, for example... Figure 4 As shown, the scanning rate of the main laser 2 is dynamically adjusted based on the monitored state information of the keyhole 24 to maintain the second steady-state keyhole, avoid insufficient or excessive energy input, and thus ensure the stability of the additive manufacturing process.

[0088] The power distribution characteristics of the main laser 2 are adjusted. Based on the monitored state information of the keyhole 24, the power distribution characteristics of the main laser 2 are dynamically adjusted to maintain the second steady-state keyhole, avoid insufficient or excessive energy input, and thus ensure the stability of the additive manufacturing process. The power distribution characteristics include, but are not limited to, the spot shape, spot size, peak power and its spatial distribution, power density distribution, pulse width, pulse frequency, pulse waveform, duty cycle, and the spatiotemporal coupled power distribution formed during the scanning process of the main laser 2.

[0089] The oscillation path of the main laser 2 is adjusted, wherein the oscillation path of the main laser 2 is dynamically adjusted based on the monitored state information of the keyhole 24 to maintain the second steady-state keyhole, avoid insufficient or excessive energy input, and thus ensure the stability of the additive manufacturing process; the oscillation path includes, but is not limited to, at least one of the following: linear oscillation, sawtooth oscillation, triangular wave oscillation, stepped oscillation, broken line oscillation, sine oscillation, cosine oscillation, circular oscillation, elliptical oscillation, figure-eight oscillation, spiral oscillation, petal oscillation, random oscillation, quasi-random oscillation, adaptive oscillation, multi-frequency superposition oscillation, amplitude or frequency gradual oscillation, and asymmetric oscillation, or any combination of the above oscillation paths;

[0090] The incident angle and polarization of the main laser 2 are adjusted. The incident angle and polarization of the main laser 2 are dynamically adjusted based on the monitored state information of the keyhole 24 to maintain the second steady-state keyhole, avoid insufficient or excessive energy input, and thus ensure the stability of the additive manufacturing process.

[0091] A wavelength-tunable main laser 1 is used, wherein the laser wavelength of the main laser 1 is dynamically adjusted based on the monitored state information of the keyhole 24 to maintain the second steady-state keyhole, avoid insufficient or excessive energy input, and thus ensure the stability of the additive manufacturing process.

[0092] An auxiliary heat source is introduced (auxiliary laser 5 or off-axis auxiliary heat source 10 or resistance heater 16), wherein, for example Figure 5 As shown, the energy output of the auxiliary heat source (auxiliary laser 5, or off-axis auxiliary heat source 10, or resistance heater 16) is dynamically adjusted based on the monitored state information of the keyhole 24 to maintain the second steady-state keyhole, avoid insufficient or excessive energy input, and thus ensure the stability of the additive manufacturing process. The auxiliary heat source is used to adjust the energy input entering the molten pool, including but not limited to at least one of coaxial laser, off-axis laser, electron beam, plasma beam, electric arc, hot lamp, hot airflow heater, resistance heater, induction heater, infrared heater, microwave heater, and ultrasonic heater, or any combination of the above auxiliary heat sources.

[0093] Or / and, change the printing environment, wherein the printing environment is dynamically adjusted based on the monitored state information of the keyhole 24 to maintain the second steady-state keyhole, avoid insufficient or excessive energy input, thereby ensuring the stability of the additive manufacturing process; the printing environment includes, but is not limited to, at least one of the following: gas type, gas composition, gas temperature, gas flow rate, oxygen content, oxygen partial pressure, chamber pressure, chamber temperature, and material surface treatment and modification, or any combination of the above printing environments.

[0094] The above-mentioned method monitors the status information of the keyhole 24 and dynamically adjusts at least one printing parameter of the main laser 2, the auxiliary heat source (auxiliary laser 5 or off-axis auxiliary heat source 10 or resistance heater 16) and / or the printing environment to ensure that the second steady-state keyhole remains stable, thereby achieving high energy utilization and high-quality forming of complex components.

[0095] In some embodiments, the second steady-state keyhole can be switched between different steady-state keyholes according to manufacturing requirements (see [link]). Figure 6 Phases III to V):

[0096] At least one structural feature of the keyhole structure of the steady-state keyhole before and after the switch remains stable for a period of time before and after the switch; the structural features include, but are not limited to, morphology, depth, width, aspect ratio, length, area, volume, front wall angle, curvature, roughness, velocity, amplitude, frequency, temperature, pressure, oxygen content, distribution, gradient, elemental composition, evaporation rate, light absorptivity and fluctuation.

[0097] Or / and, at least one of the structural features of the molten pool, steam plume, plasma, splash, ambient atmosphere, chamber environment, solidification structure, etc., corresponding to the steady-state keyhole before and after the switch respectively, remain stable for a period of time before and after the switch; the structural features include, but are not limited to, morphology, size, quantity, overlap, trajectory, surface properties, state, velocity, amplitude, frequency, temperature, pressure, composition, density, oxygen content, distribution, gradient, elemental composition, type, grain size, orientation, phase composition, precipitates, defects, subgrain structure, microstructure uniformity, residual stress and fluctuations;

[0098] Manufacturing requirements include, but are not limited to, changes or adjustments to at least one of the following: material type, morphology, size, quantity, surface properties, state, composition, density, oxygen content, distribution, gradient within the forming area, and the size, wall thickness, layer thickness, internal channels, surface properties, support, chamfer, pore structure, grid structure, gradient structure, solidification structure, mechanical properties, corrosion properties, optical properties, acoustic properties, electrical properties, magnetic properties, thermal properties, and biological properties within the forming area.

[0099] in, Figure 6 The diagram illustrates the change in the output power of the main laser 1 during the second steady-state keyhole switching and maintenance phase (i.e., phase IV and phase V): the main laser 1 gradually increases its output power to a suitable value to form a new second steady-state keyhole, and then dynamically adjusts the output power of the main laser 1 based on the monitored keyhole 24 state information to maintain the second steady-state keyhole after switching.

[0100] By switching between different steady-state keyholes according to manufacturing needs, the additive manufacturing process can be made more stable, which can effectively improve the accuracy of additive manufacturing and reduce the defect rate, thereby helping to form high-quality complex components.

[0101] In some embodiments, an in-situ monitoring device is used to monitor the keyhole state information in the molten pool 23. The monitoring information includes, but is not limited to, at least one of the following: optical signals, acoustic signals, electrical signals, magnetic signals, thermal signals, mechanical signals, geometric morphology signals, chemical composition signals, radiation signals, fluid flow field signals, phase and microstructure signals, and time and process characteristic signals. Thus, in-situ monitoring can be achieved through a single monitoring signal or through multi-modal signals (such as using optical signal 6 to monitor morphology and combining it with thermal signals to monitor temperature) to comprehensively determine the keyhole state in the molten pool 23. The acquired monitoring information is used as data input for monitoring the main laser 2 and the auxiliary heat source (auxiliary laser 5 or a side laser). The auxiliary heat source 10 or resistance heater 16) and / or the printing environment are dynamically adjusted to ensure that the second steady-state keyhole remains stable, thereby improving the reliability of forming; the in-situ monitoring device includes, but is not limited to, at least one of the following: X-ray imaging device, X-ray scattering and diffraction device, optical coherence tomography device, molten pool monitoring camera, infrared camera, visible light camera, ultraviolet camera, laser interferometer, spectrometer, plasma radiation monitoring device, pyrometer, thermocouple, photodiode, acoustic monitoring device, microphone, thermionic detection device, eddy current detection device, magneto-optical imaging device, integrating sphere, oxygen content sensor, gas composition analyzer, pressure sensor, or any combination of the above monitoring devices.

[0102] The keyhole status information includes, but is not limited to, at least one of the observation, measurement, and inference information regarding the keyhole structure's morphology, depth, width, aspect ratio, length, area, volume, front wall angle, curvature, roughness, velocity, amplitude, frequency, temperature, pressure, oxygen content, distribution, gradient, elemental composition, evaporation rate, light absorptivity, fluctuations, and their respective changes, or / and, at least one of the observation, measurement, and inference information regarding optical signals, acoustic signals, electrical signals, magnetic signals, thermal signals, mechanical signals, geometric morphology signals, chemical composition signals, radiation signals, fluid flow field signals, phase and microstructure signals, and time and process characteristic signals, etc., generated by one or more of the structures or objects corresponding to the keyhole structure, such as molten pool, steam plume, plasma, splash, ambient atmosphere, chamber environment, and solidification structure.

[0103] In some embodiments, at least one printing parameter in the main laser 2, auxiliary heat source (auxiliary laser 5 or off-axis auxiliary heat source 10 or resistance heater 16) and / or printing environment is dynamically adjusted based on the monitored state information of the keyhole 24. The printing parameters include, but are not limited to, power, scanning rate, spot shape, spot size, peak power, peak distribution, pulse width, pulse frequency, pulse waveform, duty cycle, gas type, gas composition, gas temperature, gas flow rate, oxygen content, oxygen partial pressure, chamber pressure, chamber temperature, and material surface treatment and modification.

[0104] In some embodiments, this high-energy-efficiency laser additive manufacturing method is applicable to single-laser additive manufacturing systems, multi-laser additive manufacturing systems, and composite high-energy-beam additive manufacturing systems with lasers as the primary heat source. Specifically, this high-energy-efficiency laser additive manufacturing method can be used independently as a module in single-laser additive manufacturing systems, multi-laser additive manufacturing systems, and composite high-energy-beam additive manufacturing systems with lasers as the primary heat source, and is suitable for high-efficiency and high-quality printing of components.

[0105] A second aspect of the present invention also proposes a high-energy-efficiency laser additive manufacturing system.

[0106] According to a second aspect embodiment of the present invention, a high energy efficiency laser additive manufacturing system utilizes the high energy efficiency laser additive manufacturing method of the first aspect embodiment of the present invention. For example, this high energy efficiency laser additive manufacturing system can be... Figure 1 The laser powder bed melting system 100 shown can also be Figure 2 The laser-directed energy deposition system 200 shown is illustrated.

[0107] Since the high energy efficiency laser additive manufacturing system of the second aspect embodiment of the present invention utilizes the high energy efficiency laser additive manufacturing method of the first aspect embodiment of the present invention, the high energy efficiency laser additive manufacturing system of the second aspect embodiment of the present invention has essentially the same technical effects as the high energy efficiency laser additive manufacturing method of the first aspect embodiment of the present invention, and will not be described again here.

[0108] like Figure 1As shown, the specific operation process of a high-energy-efficiency laser additive manufacturing method applicable to a laser powder bed melting system 100 is given below. The laser powder bed melting system 100 includes a main laser 1, a main laser 2, a first dichroic mirror 31, a second dichroic mirror 32, an auxiliary laser 4, an auxiliary laser 5, a coaxial monitoring device 7, a scanning galvanometer 8, a focusing lens 9 (also called a crop lens), a paraxial auxiliary heat source 10, a paraxial monitoring device 11, a forming chamber 12, a powder bed 13, a printing component 14, a forming platform 15, a resistance heater 16, a first lead screw 171, a second lead screw 172, a powder supply platform 18, a powder supply chamber 19, a scraper 20, and powder material 21.

[0109] First, the forming platform 15 is preheated using an auxiliary heat source (auxiliary laser 5, or off-axis auxiliary heat source 10, or resistance heater 16), which can increase the initial temperature of the material and its absorption rate of the laser.

[0110] The height of the powder supply platform 18 is controlled by the first lead screw 171, and the height of the forming platform 15 is controlled by the second lead screw 172. The powder material 21 in the powder supply chamber 19 is scraped into the forming chamber 12 by the scraper 20 to form a powder bed 13.

[0111] The main laser 1 outputs the main laser 2, which is reflected by the scanning galvanometer 8 and focused by the focusing lens 9 before acting on the powder bed 13 on the forming platform 15. The auxiliary laser 4 outputs the auxiliary laser 5, which is reflected by the first dichroic mirror 31, the scanning galvanometer 8, and the focusing lens 9 before acting on the powder bed 13 on the forming platform 15. The auxiliary laser 5 can have a different wavelength than the main laser 2 or the same wavelength as the main laser 2. When the wavelength of the auxiliary laser 5 is different from that of the main laser 2, the first dichroic mirror 31 should ensure that the main laser 2 is almost completely transmitted while ensuring that the auxiliary laser 5 is almost completely reflected. When the wavelength of the auxiliary laser 5 is the same as that of the main laser 2, the first dichroic mirror 31 is replaced by a polarization beam combiner.

[0112] By adjusting the energy density / power distribution / wavelength range of the main laser 2 over a period of time, introducing an auxiliary heat source (auxiliary laser 5 or off-axis auxiliary heat source 10 or resistance heater 16) and / or changing the printing environment, the formation of a first steady-state keyhole is promoted in the molten pool 23 of the current deposited layer on the forming platform 15.

[0113] The coaxial monitoring device 7 or the off-axis monitoring device 11 is used to monitor one or more of the following signals during the laser additive manufacturing process: optical signals, acoustic signals, electrical signals, magnetic signals, thermal signals, mechanical signals, geometric morphology signals, chemical composition signals, radiation signals, fluid flow field signals, phase and microstructure signals, and time and process characteristic signals, in order to obtain the status information of the keyhole 24. When the coaxial monitoring device 7 is used to monitor the optical signal 6, the second dichroic mirror 32 should ensure that the main laser 2 and the auxiliary laser 5 are almost completely transmitted, while ensuring that the optical signal 6 is almost completely reflected.

[0114] Based on the monitored keyhole 24 status information, the main laser 2, the auxiliary heat source (auxiliary laser 5 or off-axis auxiliary heat source 10 or resistance heater 16) and / or at least one printing parameter in the printing environment are dynamically adjusted. The printing parameters include, but are not limited to, power, scanning rate, spot shape, spot size, peak power, peak distribution, pulse width, pulse frequency, pulse waveform, duty cycle, gas type, gas composition, gas temperature, gas flow rate, oxygen content, oxygen partial pressure, chamber pressure, chamber temperature and material surface treatment and modification, in order to maintain the second steady-state keyhole.

[0115] Introducing a steady-state keyhole into the molten pool 23 increases the number of reflections and absorptions of the main laser 2 on the local liquid material surface, and also increases the incident angle of the main laser 2 relative to the local liquid material surface, thereby improving the overall energy utilization rate of laser additive manufacturing. This is not limited to the type of main laser 1 or the wavelength of the main laser 2, nor is it limited to the type and size of the powder material 21; by introducing a steady-state keyhole, the overall energy utilization rate of laser additive manufacturing can be improved. For example, using this technology, a conventional (near) infrared main laser 1 can be used to achieve highly efficient additive manufacturing of components made of high-reflectivity materials such as aluminum and aluminum alloys, copper and copper alloys, silver and silver alloys, and gold and gold alloys.

[0116] Repeat the above steps to complete the additive manufacturing process by depositing material layer by layer to form the printed part 14.

[0117] like Figure 2 As shown, the specific operation process of a high-energy-efficiency laser additive manufacturing method suitable for a laser-directed energy deposition system 200 is given below. The laser-directed energy deposition system 200 includes a main laser 1, a main laser 2, a first dichroic mirror 31, a second dichroic mirror 32, an auxiliary laser 4, an auxiliary laser 5, a coaxial monitoring device 7, a focusing lens 9, a paraxial auxiliary heat source 10, a paraxial monitoring device 11, a printing component 14, a forming platform 15, a resistance heater 16, powder material 21, and a nozzle 25.

[0118] First, the forming platform 15 is preheated using an auxiliary heat source (auxiliary laser 5, or off-axis auxiliary heat source 10, or resistance heater 16), which can increase the initial temperature of the material and its absorption rate of the laser.

[0119] By adjusting the energy density / power distribution / wavelength range of the main laser 2 over a period of time, introducing an auxiliary heat source (auxiliary laser 5 or off-axis auxiliary heat source 10 or resistance heater 16) and / or changing the printing environment, the formation of a first steady-state keyhole is promoted in the molten pool 23 of the current deposited layer on the forming platform 15.

[0120] The coaxial monitoring device 7 or the off-axis monitoring device 11 is used to monitor one or more of the following signals during the laser additive manufacturing process: optical signals, acoustic signals, electrical signals, magnetic signals, thermal signals, mechanical signals, geometric morphology signals, chemical composition signals, radiation signals, fluid flow field signals, phase and microstructure signals, and time and process characteristic signals, in order to obtain the status information of the keyhole 24.

[0121] Based on the monitored keyhole 24 status information, the main laser 2, the auxiliary heat source (auxiliary laser 5 or off-axis auxiliary heat source 10 or resistance heater 16) and / or at least one printing parameter in the printing environment are dynamically adjusted. The printing parameters include, but are not limited to, power, scanning rate, spot shape, spot size, peak power, peak distribution, pulse width, pulse frequency, pulse waveform, duty cycle, gas type, gas composition, gas temperature, gas flow rate, oxygen content, oxygen partial pressure, chamber pressure, chamber temperature and material surface treatment and modification, in order to maintain the second steady-state keyhole.

[0122] At the same time, the powder material 21 enters the molten pool 23 through the nozzle 25 to complete the material deposition.

[0123] Introducing a steady-state keyhole into the molten pool 23 increases the number of reflections and absorptions of the main laser 2 on the local liquid material surface, and also increases the incident angle of the main laser 2 relative to the local liquid material surface, thereby improving the overall energy utilization rate of laser additive manufacturing. This is not limited to the type of main laser 1 or the wavelength of the main laser 2, nor is it limited to the type and size of the powder material 21; by introducing a steady-state keyhole, the overall energy utilization rate of laser additive manufacturing can be improved. For example, using this technology, a conventional (near) infrared main laser 1 can be used to achieve highly efficient additive manufacturing of components made of high-reflectivity materials such as aluminum and aluminum alloys, copper and copper alloys, silver and silver alloys, and gold and gold alloys.

[0124] Repeat the above steps to complete the additive manufacturing process by depositing material layer by layer to form the printed part 14.

[0125] Three application examples are given below.

[0126] Example 1

[0127] refer to Figure 1 This embodiment provides a high-energy-efficiency laser additive manufacturing method suitable for high-reflectivity material components such as rocket engine thrust chambers, injectors, and nozzle extensions.

[0128] The forming platform 15 is preheated using a resistance heater 16.

[0129] The height of the powder supply platform 18 is controlled by the first lead screw 171 and the height of the forming platform 15 is controlled by the second lead screw 172. The powder material 21 in the powder supply chamber 19 is scraped into the forming chamber 12 by the scraper 20 to form a powder bed 13.

[0130] The (near) infrared main laser 1 is turned on to output the main laser 2. The main laser 2 is reflected by the scanning galvanometer 8 and focused by the focusing lens 9 and then acts on the powder bed 13 on the forming platform 15.

[0131] First, the scanning rate of the main laser 2 is set to zero. Then, the scanning rate of the main laser 2 is gradually increased to a suitable value to promote the formation of a first steady-state keyhole in the molten pool 23. The state of the keyhole 24 is monitored using an optical coherence tomography device. Based on the monitored keyhole state information, the power of the main laser 2 is dynamically adjusted to switch to and maintain a second steady-state keyhole.

[0132] Repeat the above steps to complete the powder bed melt additive manufacturing process through layer-by-layer deposition.

[0133] Example 2

[0134] refer to Figure 1 This embodiment provides a high-energy-efficiency laser additive manufacturing method for scenarios with limited energy or power, such as rapid replacement of deep space exploration components, in-situ repair of vulnerable parts in seabed operations, and customization of military field equipment.

[0135] The forming platform 15 is preheated using a resistance heater 16.

[0136] The height of the powder supply platform 18 is controlled by the first lead screw 171 and the height of the forming platform 15 is controlled by the second lead screw 172. The powder material 21 in the powder supply chamber 19 is scraped into the forming chamber 12 by the scraper 20 to form a powder bed 13.

[0137] The main laser 1 with tunable wavelength is turned on and outputs the main laser 2. The main laser 2 is reflected by the scanning galvanometer 8 and focused by the focusing lens 9 and then acts on the powder bed 13 on the forming platform 15.

[0138] First, the main laser 1 is set to output a short-wavelength laser, or output a laser wavelength that matches the high laser absorptivity. Then, the laser wavelength of the main laser 2 is gradually increased to a suitable value, or the laser wavelength is gradually adjusted to a suitable value that matches the low laser absorptivity, so as to promote the formation of a first stable keyhole in the molten pool 23. The state of the keyhole 24 is monitored using an optical coherence tomography device, and the power of the main laser 2 is dynamically adjusted based on the monitored keyhole state information to switch to and maintain a second stable keyhole.

[0139] Repeat the above steps to complete the powder bed melt additive manufacturing process through layer-by-layer deposition.

[0140] Example 3

[0141] refer to Figure 1 This embodiment provides a high-energy-efficiency laser additive manufacturing method suitable for precious metal jewelry or parts such as gold and gold alloys, silver and silver alloys.

[0142] The forming platform 15 is preheated using a resistance heater 16.

[0143] The height of the powder supply platform 18 is controlled by the first lead screw 171 and the height of the forming platform 15 is controlled by the second lead screw 172. The powder material 21 in the powder supply chamber 19 is scraped into the forming chamber 12 by the scraper 20 to form a powder bed 13.

[0144] Turn on the (near)infrared main laser 1 and auxiliary laser 4. First, control the power of the auxiliary laser 4 to keep it at a constant value. Then, gradually reduce the output power of the auxiliary laser 4 until it is zero to promote the formation of a first steady-state keyhole in the molten pool 23. Use an optical coherence tomography device to monitor the state of the keyhole 24. Based on the monitored keyhole state information, dynamically adjust the power of the main laser 2 to switch to and maintain a second steady-state keyhole.

[0145] Repeat the above steps to complete the powder bed melt additive manufacturing process through layer-by-layer deposition.

[0146] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

[0147] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A high-energy-efficiency laser additive manufacturing method, characterized in that, Applicable to laser powder bed melting and directional energy deposition processes, including the following steps: S1: By adjusting the energy density / power distribution / wavelength range of the main laser over a period of time, introducing an auxiliary heat source, and / or changing the printing environment, the formation of the first steady-state keyhole is promoted in the molten pool of the current deposited layer on the forming platform; S2: Monitor the state of the keyhole in the molten pool in real time, and dynamically adjust the main laser, auxiliary heat source and / or printing environment based on the monitored keyhole state information to switch to and maintain a second stable keyhole. The second stable keyhole may be the same as or different from the first stable keyhole. The second stable keyhole can be switched between different stable keyholes according to manufacturing requirements. S3: Repeat steps S1 and S2 to complete the additive manufacturing process by depositing layers one by one. In step S1, the adjustment method to promote the formation of the first steady-state keyhole includes at least one of the following methods, or any combination of the following methods: adjusting the output power of the main laser, adjusting the scanning rate of the main laser, adjusting the power distribution characteristics of the main laser, adjusting the swing path of the main laser, adjusting the incident angle and polarization of the main laser, using a wavelength-tunable main laser, introducing an auxiliary heat source, and changing the printing environment. Furthermore, the process is divided into a first stage and a second stage for forming the first steady-state keyhole; The adjustment of the output power of the main laser includes: in the first stage, the main laser uses a larger output power, and in the second stage, the main laser gradually reduces the output power to a suitable value; Adjusting the scanning rate of the main laser includes: using a lower scanning rate for the main laser in the first stage, and gradually increasing the scanning rate of the main laser to a suitable value in the second stage; Adjusting the power distribution characteristics of the main laser includes: in the first stage, the main laser uses a beam distribution with high energy concentration; in the second stage, the main laser gradually reduces the energy concentration of the beam distribution to a suitable value; the power distribution characteristics include the spot shape, spot size, peak power and its spatial distribution, power density distribution, pulse width, pulse frequency, pulse waveform, duty cycle, and the spatiotemporal coupled power distribution formed during the scanning process of the main laser. Adjusting the oscillation path of the main laser includes: in a first stage, adjusting the oscillation path of the main laser to prolong the interaction time between the laser and the material, and / or to increase the energy concentration of the laser; in a second stage, adjusting the oscillation path of the main laser to gradually decrease the interaction time between the laser and the material until a suitable value is reached, and / or to gradually decrease the energy concentration of the laser until a suitable value is reached; the oscillation path includes at least one of the following: linear oscillation, sawtooth oscillation, triangular wave oscillation, stepped oscillation, broken line oscillation, sine oscillation, cosine oscillation, circular oscillation, elliptical oscillation, figure-eight oscillation, spiral oscillation, petal oscillation, random oscillation, quasi-random oscillation, adaptive oscillation, multi-frequency superposition oscillation, amplitude or frequency gradual oscillation, and asymmetric oscillation, or any combination of the above oscillation paths; Adjusting the incident angle and polarization of the main laser includes: in the first stage, the main laser uses an incident angle / polarization that matches the high laser absorptivity, and in the second stage, the main laser gradually adjusts the incident angle / polarization to a suitable value that matches the low laser absorptivity. The wavelength-tunable master laser includes: in a first stage, the master laser outputs a short-wavelength laser, or outputs a wavelength laser that matches a high laser absorptivity; in a second stage, the master laser gradually increases the laser wavelength to a suitable value, or gradually adjusts the laser wavelength to a suitable value that matches a low laser absorptivity. The auxiliary heat source is introduced by: turning on the auxiliary heat source at a higher power in the first stage, and gradually reducing the power of the auxiliary heat source to a suitable value in the second stage; the auxiliary heat source is used to increase the energy input into the molten pool, and the auxiliary heat source includes at least one of coaxial laser, off-axis laser, electron beam, plasma beam, electric arc, hot lamp, hot gas heater, resistance heater, induction heater, infrared heater, microwave heater, and ultrasonic heater, or any combination of the above auxiliary heat sources; Changing the printing environment includes: in the first stage, the printing environment uses conditions that match a high laser absorptivity, and in the second stage, the printing environment is gradually adjusted to suitable conditions that match a low laser absorptivity; the printing environment includes at least one of gas type, gas composition, gas temperature, gas flow rate, oxygen content, oxygen partial pressure, chamber pressure, chamber temperature, and material surface treatment and modification, or any combination of the printing environment; One or more of the methods used in the first stage of forming the first steady-state keyhole are employed to increase the energy input into the molten pool for a period of time, or / and to increase the energy concentration into the molten pool for a period of time; One or more of the methods used in the second stage of forming the first steady-state keyhole are employed to gradually reduce the energy input into the molten pool until a suitable value is reached, or / and to gradually reduce the energy concentration into the molten pool until a suitable value is reached.

2. The high-energy-efficiency laser additive manufacturing method according to claim 1, characterized in that: In step S1, the first steady-state keyhole refers to the keyhole structure information satisfying the first preset condition and remaining stable for a period of time. The keyhole structure information includes at least one of the following: morphology, depth, width, aspect ratio, length, area, volume, front wall angle, curvature, roughness, velocity, amplitude, frequency, temperature, pressure, oxygen content, distribution, gradient, elemental composition, evaporation rate, light absorption rate, and fluctuations. In step S2, the second steady-state keyhole refers to the keyhole structure information satisfying the second preset condition and remaining stable for a period of time; the keyhole structure information includes at least one of the following: morphology, depth, width, aspect ratio, length, area, volume, front wall angle, curvature, roughness, velocity, amplitude, frequency, temperature, pressure, oxygen content, distribution, gradient, elemental composition, evaporation rate, light absorption rate, and fluctuations.

3. The high energy utilization laser additive manufacturing method according to claim 2, characterized in that: In step S1, at least one of the structural features of the molten pool, steam plume, plasma, splash, ambient atmosphere, chamber environment, and solidification structure corresponding to the first steady-state keyhole satisfies the corresponding preset conditions and remains stable for a period of time. The structural features include morphology, size, quantity, overlap, trajectory, surface properties, state, velocity, amplitude, frequency, temperature, pressure, composition, density, oxygen content, distribution, gradient, elemental composition, type, grain size, orientation, phase composition, precipitates, defects, subgrain structure, microstructure uniformity, residual stress, and fluctuations. In step S2, at least one of the structural features of the molten pool, steam plume, plasma, splash, ambient atmosphere, chamber environment, and solidification structure corresponding to the second steady-state keyhole satisfies the corresponding preset conditions and remains stable for a period of time. The structural features include morphology, size, quantity, overlap, trajectory, surface properties, state, velocity, amplitude, frequency, temperature, pressure, composition, density, oxygen content, distribution, gradient, elemental composition, type, grain size, orientation, phase composition, precipitates, defects, subgrain structure, microstructure uniformity, residual stress, and fluctuations.

4. The high-energy-efficiency laser additive manufacturing method according to claim 1, characterized in that, In step S2, the method for maintaining the second steady-state keyhole is as follows: The output power of the main laser is adjusted, wherein the output power of the main laser is dynamically adjusted based on the monitored keyhole state information in order to maintain the second steady-state keyhole. The scanning rate of the main laser is adjusted, wherein the scanning rate of the main laser is dynamically adjusted based on the monitored keyhole state information in order to maintain the second steady-state keyhole. The power distribution characteristics of the main laser are adjusted, wherein the power distribution characteristics of the main laser are dynamically adjusted based on the monitored keyhole state information to maintain the second steady-state keyhole; the power distribution characteristics include spot shape, spot size, peak power and its spatial distribution, power density distribution, pulse width, pulse frequency, pulse waveform, duty cycle, and spatiotemporal coupled power distribution formed during the scanning process of the main laser; The swing path of the main laser is adjusted, wherein the swing path of the main laser is dynamically adjusted based on the monitored keyhole state information to maintain the second steady-state keyhole; the swing path includes at least one of the following: linear swing, sawtooth swing, triangular wave swing, stepped swing, broken line swing, sine swing, cosine swing, circular swing, elliptical swing, figure-eight swing, spiral swing, petal swing, random swing, quasi-random swing, adaptive swing, multi-frequency superposition swing, amplitude or frequency gradual swing, and asymmetric swing, or any combination of the above swing paths; The incident angle and polarization of the main laser are adjusted, wherein the incident angle and polarization of the main laser are dynamically adjusted based on the monitored keyhole state information in order to maintain the second steady-state keyhole. The wavelength-tunable main laser is used, wherein the laser wavelength of the main laser is dynamically adjusted based on the monitored keyhole state information to maintain the second steady-state keyhole. The auxiliary heat source is introduced, wherein the energy output of the auxiliary heat source is dynamically adjusted based on the monitored keyhole status information to maintain the second steady-state keyhole; the auxiliary heat source is used to adjust the energy input entering the molten pool, and the auxiliary heat source includes at least one of coaxial laser, off-axis laser, electron beam, plasma beam, electric arc, hot lamp, hot air heater, resistance heater, induction heater, infrared heater, microwave heater, and ultrasonic heater, or any combination of the above auxiliary heat sources; Or / and, change the printing environment, wherein the printing environment is dynamically adjusted based on the monitored keyhole state information to maintain the second steady-state keyhole; the printing environment includes at least one of gas type, gas composition, gas temperature, gas flow rate, oxygen content, oxygen partial pressure, chamber pressure, chamber temperature and material surface treatment and modification, or any combination of the printing environment.

5. The high-energy-efficiency laser additive manufacturing method according to claim 1, characterized in that, The second steady-state keyhole can be switched between different steady-state keyholes according to manufacturing requirements: At least one structural feature of the keyhole structure of the steady-state keyhole before and after the switch remains stable for a period of time before and after the switch; the structural feature includes morphology, depth, width, aspect ratio, length, area, volume, front wall angle, curvature, roughness, velocity, amplitude, frequency, temperature, pressure, oxygen content, distribution, gradient, elemental composition, evaporation rate, light absorptivity, and fluctuations. Or / and, at least one of the structural features of the molten pool, steam plume, plasma, splash, ambient atmosphere, chamber environment, and solidification structure corresponding to the steady-state keyhole before and after the switch, respectively, remain stable for a period of time before and after the switch; the structural features include morphology, size, quantity, overlap, trajectory, surface properties, state, velocity, amplitude, frequency, temperature, pressure, composition, density, oxygen content, distribution, gradient, elemental composition, type, grain size, orientation, phase composition, precipitates, defects, subgrain structure, microstructure uniformity, residual stress, and fluctuations; The manufacturing requirements include changes or adjustments to at least one of the following: material type, morphology, size, quantity, surface properties, state, composition, density, oxygen content, distribution, gradient within the forming area, and the size, wall thickness, layer thickness, internal channels, surface properties, support, chamfer, pore structure, grid structure, gradient structure, solidification structure, mechanical properties, corrosion properties, optical properties, acoustic properties, electrical properties, magnetic properties, thermal properties, and biological properties of the forming structure.

6. The high energy utilization laser additive manufacturing method according to claim 1, characterized in that: The keyhole status information in the molten pool is monitored using an in-situ monitoring device. The monitoring information includes at least one of the following: optical signal, acoustic signal, electrical signal, magnetic signal, thermal signal, mechanical signal, geometric morphology signal, chemical composition signal, radiation signal, fluid flow field signal, phase and microstructure signal, and time and process characteristic signal. The keyhole state information includes at least one of the following: observational, measurement, and inference information regarding the keyhole structure's morphology, depth, width, aspect ratio, length, area, volume, front wall angle, curvature, roughness, velocity, amplitude, frequency, temperature, pressure, oxygen content, distribution, gradient, elemental composition, evaporation rate, light absorptivity, fluctuations, and their respective changes; or / and at least one of the following: optical signals, acoustic signals, electrical signals, magnetic signals, thermal signals, mechanical signals, geometric morphology signals, chemical composition signals, radiation signals, fluid flow field signals, phase and microstructure signals, and time and process characteristic signals.

7. The high-energy-efficiency laser additive manufacturing method according to claim 1, characterized in that, Based on the monitored keyhole status information, at least one printing parameter of the main laser, the auxiliary heat source, and / or the printing environment is dynamically adjusted; the printing parameters include power, scanning rate, spot shape, spot size, peak power, peak distribution, pulse width, pulse frequency, pulse waveform, duty cycle, gas type, gas composition, gas temperature, gas flow rate, oxygen content, oxygen partial pressure, chamber pressure, chamber temperature, and material surface treatment and modification.

8. The high-energy-efficiency laser additive manufacturing method according to claim 1, characterized in that, The high-energy-efficiency laser additive manufacturing method is applicable to single-laser additive manufacturing systems, multi-laser additive manufacturing systems, and composite high-energy beam additive manufacturing systems with lasers as the main heat source.

9. A high-energy-efficiency laser additive manufacturing system, characterized in that, The high energy efficiency laser additive manufacturing method as described in any one of claims 1 to 8 is utilized.

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