LIBS detection device and method for online monitoring nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF

Abstract

The invention relates to the field of laser powder bed melting monitoring technology and laser spectrum detection, in particular to an LIBS (laser-induced breakdown spectroscopy) detection device and method for online monitoring nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF (laser PBF), and the LIBS detection device comprises an LPBF printing unit, an LPBF laser unit, an LIBS element detection unit and a calculation control unit; the LIBS element detection unit generates pulse laser by using an Nd: YAG laser, guides the laser beam to the surface of a stainless steel sample through a beam splitter and a galvanometer, excites and generates plasma, acquires a plasma spectrum through a six-channel optical fiber spectrometer, controls the time sequence of laser emission and spectrum acquisition, and analyzes spectral data in real time; the concentration distribution of nitrogen, hydrogen and oxygen elements in the sample is detected, the printing parameters of the LPBF laser unit are dynamically adjusted according to the analysis result, and rapid and real-time online detection of the nitrogen, hydrogen and oxygen elements in the stainless steel sample in the printing process is achieved.

Description

Technical Field

[0001] The present invention relates to the fields of laser powder bed fusion monitoring technology and laser spectrum detection, and in particular to a LIBS detection device and method for online monitoring of nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF. Background Art

[0002] Laser Powder Bed Fusion (LPBF) is an advanced additive manufacturing technology primarily used for processing metal materials, particularly for printing complex shapes and high-precision metal parts. Stainless steel printed using LPBF boasts high strength, corrosion resistance, and excellent mechanical properties, making it commonly used in aerospace, medical, and industrial applications. However, even in an inert atmosphere within the LPBF print chamber, the effects of impurity gases such as nitrogen (N), hydrogen (H), and oxygen (O) cannot be completely eliminated. This is because the raw material powder may contain trace amounts of these gases, the high-temperature melting of the laser and metal powder may trigger certain microchemical reactions, and the presence of incompletely vented air in the LPBF print chamber can all contribute to excessive amounts of these gases in the LPBF-printed stainless steel alloy, impacting the material's performance. Excessive nitrogen can make stainless steel samples brittle; excessive hydrogen can lead to pores, cracks, and hydrogen embrittlement, compromising the material's mechanical properties and durability; and excessive oxygen can lead to oxide formation, reducing the material's strength. Therefore, it is of great significance to quickly monitor the content of impurity gas elements such as N, H, and O in the sample in real time during the LPBF process and to guide the LPBF printing process of stainless steel online.

[0003] Laser-induced breakdown spectroscopy (LIBS) is an analytical technique based on laser-induced plasma emission spectroscopy (LIBS), widely used for elemental composition analysis. This technique irradiates the sample surface with high-energy laser pulses, locally heating the sample to extremely high temperatures, rapidly vaporizing it and forming a plasma. During the plasma cooling process, the excited atoms and ions emit spectral lines of specific wavelengths. Analysis of these spectral lines can determine the elemental identity and concentration in the sample. LIBS is widely used in industry for its in-situ, rapid, simultaneous analysis of all elements, and remote control capabilities.

[0004] Existing methods for online monitoring of LPBF printing processes primarily include sensor monitoring, vision systems, thermal imaging, acoustic monitoring, and optical sensing. These methods provide real-time monitoring and feedback on key parameters during the printing process, such as temperature, laser power, material deposition rate, surface topography, and defect detection, to ensure product quality and process stability. However, there are no reports on the application of LIBS technology to online monitoring of impurity gases such as N, H, and O during LPBF printing.

[0005] In summary, the current LIBS monitoring of LPBF printing processes lacks a robust, unified, and effective solution for online monitoring of impurity gas elements such as N, H, and O. Therefore, the present invention aims to develop a LIBS detection device for rapid, real-time online analysis of N, H, and O in LPBF stainless steel. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that the existing LPBF stainless steel production process cannot perform real-time online detection of impurity elements such as nitrogen (N), hydrogen (H), and oxygen (O). The purpose of the present invention is to provide a LIBS detection device and method for online monitoring of nitrogen, hydrogen, and oxygen elements in LPBF stainless steel. This device and method achieve rapid, real-time online detection of nitrogen, hydrogen, and oxygen element concentrations. By linking with the LPBF printing process, the printing parameters can be dynamically adjusted, thereby improving the quality and performance stability of the printed stainless steel components.

[0007] The present invention is achieved through the following technical solutions:

[0008] A LIBS detection device for online monitoring of nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF, comprising:

[0009] LPBF printing unit, used to deliver and spread metal powder and print stainless steel samples layer by layer;

[0010] The LPBF laser unit is used to generate and control the laser beam required in the printing process and selectively scan and melt the metal powder layer;

[0011] LIBS element detection unit, used to emit pulsed laser to ablate the stainless steel sample printed layer by layer to generate plasma and collect the LIBS spectrum emitted by the plasma;

[0012] A calculation control unit is electrically connected to the LIBS element detection unit and the LPBF laser unit. The calculation control unit is used to control the emission time of the pulsed laser and the collection timing of the LIBS spectrum, and analyze the collected LIBS spectrum.

[0013] The laser beams emitted by the LPBF laser unit and the LIBS element detection unit are both injected into the stainless steel sample in the printing state in the LPBF printing unit.

[0014] Specifically, the LPBF printing unit includes: a powder feeding area, a printing area and a powder spreading scraper. Metal powder is set in the powder feeding area, and the stainless steel sample obtained by layer-by-layer printing is located in the printing area. The powder spreading scraper is set between the powder feeding area and the printing area, and is used to horizontally move the metal powder in the powder feeding area to the printing area and evenly spread it. The laser beams emitted by the LPBF laser unit and the LIBS element detection unit are both shot into the stainless steel sample in the printing area.

[0015] Specifically, the powder feeding area includes: a powder feeding chamber and a powder feeding piston, the metal powder is arranged in the powder feeding chamber, the powder feeding piston is arranged in the powder feeding chamber and located below the metal powder, and the powder feeding piston pushes the metal powder to move upward;

[0016] The printing area includes: a printing cavity and a printing piston. Waste powder is set in the printing cavity. The stainless steel sample in the printing state is placed on the waste powder. The printing piston is set in the printing cavity and located below the waste powder. The printing piston pushes the waste powder downward.

[0017] Specifically, the LPBF laser unit includes: a galvanometer, an LPBF continuous laser, a dichroic mirror and an LPBF control box;

[0018] The galvanometer is arranged above the stainless steel sample, the LPBF laser beam emitted by the LPBF continuous laser is transmitted through the dichroic mirror and focused by the galvanometer to form an LPBF printing focused laser, and the LPBF control box is electrically connected to the LPBF continuous laser and the galvanometer;

[0019] The dichroic mirror is used to transmit the LPBF laser beam and reflect light of other wavelength bands. The LPBF control box is used to control the emission of the LPBF laser beam and the scanning path of the galvanometer.

[0020] Specifically, the LIBS element detection unit includes: a beam splitter, an Nd:YAG laser, a LIBS spectral focusing lens and a six-channel fiber optic spectrometer;

[0021] The LIBS laser beam emitted by the Nd:YAG laser is reflected by the dichroic mirror and the beam splitter, and is focused by the galvanometer to form a LIBS excitation focused laser; the beam splitter is used to reflect the LIBS laser beam and transmit light of other wavelength bands;

[0022] The LIBS spectrum focusing lens is used to collect the LIBS spectrum emitted by the plasma excited by the LIBS excitation focused laser on the surface of the stainless steel sample, and guide the LIBS spectrum to the six-channel fiber optic spectrometer;

[0023] The LIBS spectrum is reflected by the galvanometer and the dichroic mirror, and then passes through the beam splitter to enter the LIBS spectrum focusing lens.

[0024] Optionally, the LPBF continuous laser emits 1064nm laser, and the Nd:YAG laser emits 532nm pulsed laser;

[0025] The dichroic mirror transmits 1064nm laser light and reflects 532nm laser light and visible light; the beam splitter is a 532nm beam splitter;

[0026] The optical axis of the dichroic mirror and the optical axis of the beam splitter form an angle of 45° with the propagation path of the laser beam.

[0027] Specifically, the calculation control unit includes: a timing controller and a computer;

[0028] The timing controller is electrically connected to the Nd:YAG laser and the six-channel fiber spectrometer, and the timing controller is used to control the timing of the Nd:YAG laser emitting the LIBS laser beam and the timing of the spectrum acquisition of the six-channel fiber spectrometer;

[0029] The computer is electrically connected to the timing controller, the LPBF laser unit and the LPBF printing unit. The computer is used to coordinate the LPBF laser unit and the LPBF printing unit to work together, and is used to receive spectrum data and analyze LIBS spectra.

[0030] Furthermore, the LIBS element detection unit further includes: a reflector, which is arranged on the optical path between the beam splitter and the LIBS spectrum focusing mirror, and is used to reflect the LIBS spectrum to the LIBS spectrum focusing mirror.

[0031] A LIBS detection method for online monitoring of nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF, the method comprising: a printing method and a detection method;

[0032] The printing method comprises:

[0033] The three-dimensional printing model of the stainless steel component is input into the calculation control unit, and the calculation control unit sends printing and detection control instructions to the LPBF laser unit and the LIBS element detection unit;

[0034] The LPBF laser unit, according to the instructions of the calculation control unit, guides the LPBF laser beam through the galvanometer to scan and selectively melt the metal powder layer layer by layer, forming a stainless steel component stacked layer by layer;

[0035] The detection method comprises:

[0036] During the printing process of each layer, the LIBS element detection unit uses an Nd:YAG laser to emit a LIBS laser beam, which is guided and focused onto the surface of the printed layer through a dichroic mirror, a beam splitter, and a galvanometer to stimulate and generate plasma.

[0037] The LIBS spectrum emitted by the plasma is reflected by the galvanometer and beam splitter, then guided by the LIBS spectral focusing lens to a six-channel fiber optic spectrometer for collection. The six-channel fiber optic spectrometer converts the spectral signal into an electrical signal and transmits it to the calculation control unit.

[0038] The calculation control unit performs real-time analysis on the collected LIBS spectra to detect the concentration distribution of N, H, and O elements.

[0039] Specifically, the method for performing layer-by-layer printing includes:

[0040] The powder feeding piston is used to push the metal powder in the powder feeding chamber upward, and the powder spreading scraper is used to evenly spread the powder into the printing chamber to form a powder layer;

[0041] The galvanometer guides the LPBF laser beam according to a preset scanning path to selectively melt the metal powder on the surface of the printed layer, causing it to solidify to form a layer of the printed component;

[0042] After the printing of this layer is completed, the printing piston is used to push the printing chamber down one layer;

[0043] Repeat all the above steps until the stainless steel component is printed layer by layer.

[0044] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0045] The present invention proposes an online detection device and method that combines laser powder bed fusion (LPBF) technology with laser-induced breakdown spectroscopy (LIBS) technology. The LIBS element detection unit uses an Nd:YAG laser to generate pulsed laser light. The laser beam is guided to the surface of a stainless steel sample via a beam splitter and a galvanometer to stimulate and generate plasma. The plasma spectrum is then collected using a six-channel fiber optic spectrometer. A computational control unit controls the timing of laser emission and spectrum acquisition, and performs real-time analysis of the spectral data to detect the concentration distribution of nitrogen, hydrogen, and oxygen elements in the sample. The printing parameters of the LPBF laser unit are dynamically adjusted based on the analysis results. This enables rapid, real-time online detection of nitrogen, hydrogen, and oxygen elements in the stainless steel sample during the printing process, thereby effectively avoiding the problem of material performance degradation caused by excessive concentrations of impurity elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings illustrate exemplary embodiments of the present invention and, together with the description thereof, are used to explain the principles of the present invention. These drawings are included to provide a further understanding of the present invention, and the accompanying drawings are included in and constitute a part of this specification and do not constitute a limitation of the embodiments of the present invention.

[0047] Figure 1 The figure is a schematic structural diagram of a LIBS detection device for online monitoring of nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF according to the present invention.

[0048] Figure 2 Schematic diagram of plasma generation monitored by LIBS during LPBF printing according to the present invention.

[0049] Figure 3 Schematic diagram of the N element spectrum line in the LIBS signal collected according to the present invention.

[0050] Figure 4 Schematic diagram of H element spectrum lines in the LIBS signal collected according to the present invention.

[0051] Figure 5 Schematic diagram of the O element spectrum line in the LIBS signal collected according to the present invention.

[0052] Figure 1: 1-powder feeding piston, 2-powder feeding chamber, 3-powder spreading scraper, 4-printing piston, 5-printing chamber, 6-stainless steel sample, 7-plasma, 8-LIBS excitation focusing laser, 9-LPBF printing focusing laser, 10-galvanometer, 11-LPBF laser beam, 12-LPBF continuous laser, 13-dichroic mirror, 14-LIBS laser beam, 15-beam splitter, 16-LIBS spectrum, 17-reflector, 18-Nd:YAG laser, 19-six-channel fiber optic spectrometer, 20-LIBS spectrum focusing mirror, 21-computer, 22-timing controller, 23-LPBF control box. DETAILED DESCRIPTION

[0053] To make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the relevant content and are not intended to limit the present invention.

[0054] It should also be noted that, for the convenience of description, only the parts related to the present invention are shown in the drawings.

[0055] In the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0056] Example 1

[0057] A LIBS detection device for online monitoring of nitrogen, hydrogen, and oxygen in stainless steel produced using LPBF (Low-Potassium Fluoride) technology. Its operating principle is based on the layer-by-layer LPBF printing process of stainless steel components, combined with LIBS technology to achieve real-time detection of key elements (N, H, and O) in the sample during each layer's printing. The device achieves simultaneous printing and detection through the collaboration of multiple units, including an LPBF printing unit, an LPBF laser unit, a LIBS element detection unit, and a computational control unit.

[0058] The LPBF printing unit is used to deliver and spread metal powder, and to print the stainless steel sample 6 layer by layer. Through a series of mechanical actions, such as the upward movement of the powder feeding piston 1, the horizontal movement of the scraper, and the downward movement of the printing piston 4, the uniform laying of each layer of metal powder and the layer-by-layer formation of the sample are ensured.

[0059] The LPBF laser unit is used to generate and control the laser beam required in the printing process, and accurately guides the laser beam through the galvanometer 10 to selectively scan and melt the metal powder layer.

[0060] The LIBS element detection unit is used to emit a pulsed laser to ablate the layer-by-layer printed stainless steel sample 6 to generate plasma 7 and collect the LIBS spectrum 16 emitted by the plasma 7. The plasma 7 is formed by pulsed laser ablation on the surface of the stainless steel sample 6. When the plasma 7 cools, it emits a spectral signal of a specific wavelength, reflecting the concentration of elements such as N, H, and O in the sample.

[0061] The calculation control unit is electrically connected to the LIBS element detection unit and the LPBF laser unit. The calculation control unit is used to control the emission time of the pulsed laser and the acquisition timing of the LIBS spectrum 16 , and analyze the acquired LIBS spectrum 16 .

[0062] The laser beams emitted by the LPBF laser unit and the LIBS element detection unit are both incident on the stainless steel sample 6 in the printing state in the LPBF printing unit.

[0063] This embodiment integrates LIBS technology into the LPBF printing process, achieving seamless collaboration between printing and testing. The LPBF printing unit ensures the accuracy of each layer of sample printing, while the LIBS element detection unit provides real-time elemental analysis. The computational control unit coordinates the printing and testing processes and enables process optimization.

[0064] Example 2

[0065] like Figure 1 and Figure 2 As shown, this embodiment provides a specific structure.

[0066] First, the structural composition and functions of the LPBF printing unit are provided to achieve metal powder transportation and uniform laying during the layer-by-layer printing process of stainless steel.

[0067] The LPBF printing unit includes a powder feeding area, a printing area, and a powder spreading scraper 3. The powder feeding area is filled with metal powder, and the stainless steel sample 6, obtained by layer-by-layer printing, is placed in the printing area. The powder spreading scraper 3 is located between the powder feeding area and the printing area, and is used to horizontally move the metal powder in the powder feeding area to the printing area and evenly spread it. The laser beams emitted by the LPBF laser unit and the LIBS element detection unit are both directed into the stainless steel sample 6 in the printing area. The LPBF laser unit selectively melts the metal powder in the printed layer to achieve layer-by-layer sample formation. The LIBS element detection unit is used to excite plasma 7 for spectral detection.

[0068] The powder feeding area includes: a powder feeding chamber 2 and a powder feeding piston 1. The metal powder is set in the powder feeding chamber 2. The powder feeding piston 1 is set in the powder feeding chamber 2 and is located below the metal powder. The powder feeding piston 1 pushes the metal powder upward;

[0069] The printing area includes: a printing chamber 5 and a printing piston 4. Waste powder is set in the printing chamber 5. The stainless steel sample 6 in the printing state is placed on the waste powder. The printing piston 4 is set in the printing chamber 5 and is located below the waste powder. The printing piston 4 pushes the waste powder downward. The waste powder is actually unused metal powder pushed from the powder feeding chamber 2.

[0070] The powder feeding chamber 2 is used to store the metal powder to be printed; the powder feeding piston 1 controls the powder supply to the powder feeding chamber 2 to ensure uniform powder supply during the printing process; the powder spreading scraper 3 evenly scrapes the powder from the powder feeding chamber 2 to the printing chamber 5, providing a uniform powder layer for laser scanning; the printing chamber 5 is a container for waste powder and formed components; after printing a layer of sample, the printing piston 4 pushes the printing chamber 5 down evenly by one layer to ensure that the height of each layer of the component is consistent; the stainless steel sample 6 is a component printed by the LPBF laser and is also the target of online detection by the LIBS element detection unit.

[0071] The LPBF laser unit achieves selective melting of the metal powder layer through precise optical path guidance of the galvanometer 10 and the dichroic mirror 13, as well as high-energy laser input from the LPBF continuous laser 12. The LPBF laser unit includes: a galvanometer 10, an LPBF continuous laser 12, a dichroic mirror 13, and an LPBF control box 23; the LPBF continuous laser 12 emits a 1064nm laser, and the dichroic mirror 13 transmits the 1064nm laser and reflects the 532nm laser and visible light.

[0072] The galvanometer 10 is set above the stainless steel sample 6. The LPBF laser beam 11 emitted by the LPBF continuous laser 12 is transmitted through the dichroic mirror 13 and focused by the galvanometer 10 to form the LPBF printing focused laser 9. The LPBF control box 23 is electrically connected to the LPBF continuous laser 12 and the galvanometer 10.

[0073] The dichroic mirror 13 is used to transmit the LPBF laser beam 11 and reflect light of other wavelength bands. The LPBF control box 23 is used to control the emission of the LPBF laser beam 11 and the scanning path of the galvanometer 10 .

[0074] The galvanometer 10 is composed of two high-precision lenses, which control the laser scanning paths of the X-axis and Y-axis respectively. It can quickly and accurately guide the LPBF laser beam 11 to scan the surface of the powder layer of the printing cavity 5, so that each layer of powder is melted and solidified; the LPBF continuous laser 12 is the printing laser source in the LPBF system, with a wavelength of 1064nm. The high-energy laser beam it emits is reflected by the galvanometer 10 to selectively heat and melt the powder layer of the printing cavity 5; the dichroic mirror 13 can transmit the 1064nm laser emitted by the LPBF continuous laser 12 and reflect light of other wavelengths at the same time, thereby separating the laser optical path of the LPBF continuous laser 12 and the laser optical path of the LIBS element detection unit; the LPBF control box 23 is responsible for the management and control of the entire LPBF printing process, coordinating the work of the LPBF laser unit and the LPBF printing unit to ensure the smooth progress of the printing process.

[0075] The LIBS element detection unit uses the pulsed laser generated by the Nd:YAG laser 18 to achieve efficient ablation of the sample surface and excitation of the plasma 7. Combined with the optical path separation function of the dichroic mirror 13 and the beam splitter 15, as well as the precise focusing of the galvanometer 10, the efficient transmission of the LIBS laser and the pure collection of the spectral signal are ensured. Finally, through the collaboration of the LIBS spectrum 16 focusing lens and the six-channel fiber spectrometer 19, the unit can accurately detect the concentration of elements such as nitrogen, hydrogen, and oxygen in the stainless steel sample 6 in real time. The LIBS element detection unit includes: a beam splitter 15, an Nd:YAG laser 18, a LIBS spectrum 16 focusing lens and a six-channel fiber spectrometer 19; the Nd:YAG laser 18 emits a 532nm pulsed laser; the beam splitter 15 is a 532nm beam splitter;

[0076] The LIBS laser beam 14 emitted by the Nd:YAG laser 18 is reflected by the dichroic mirror 13 and the beam splitter 15, and is focused by the galvanometer 10 to form the LIBS excitation focused laser 8; the beam splitter 15 is used to reflect the LIBS laser beam 14 and transmit light of other wavelength bands;

[0077] The LIBS spectrum 16 focusing lens is used to collect the LIBS spectrum 16 emitted by the plasma 7 excited by the LIBS excitation focused laser 8 on the surface of the stainless steel sample 6, and guide the LIBS spectrum 16 to the six-channel fiber optic spectrometer 19;

[0078] After being reflected by the galvanometer mirror 10 and the dichroic mirror 13, the LIBS spectrum 16 passes through the beam splitter 15 and enters the focusing lens of the LIBS spectrum 16. The optical axes of the dichroic mirror 13 and the beam splitter 15 form a 45° angle with the propagation path of the laser beam.

[0079] The optical axis of the beam splitter 15 forms a 45° angle with the 532nm pulsed laser and is arranged in the reflection light path of the 1064nm dichroic mirror, reflecting the 532nm pulsed laser and transmitting spectra of other bands; the LIBS spectrum focusing mirror 20 is used to receive the LIBS spectrum 16 and guide it to the six-channel fiber optic spectrometer 19; the six-channel fiber optic spectrometer 19 converts the LIBS spectrum 16 into an electrical signal and transmits it to the computer 21 for spectral line analysis.

[0080] The computational control unit achieves precise synchronization between LIBS laser triggering and spectrum acquisition through the timing controller 22, and achieves high coordination between LPBF printing and detection and real-time processing of spectrum data through the computer 21. The computational control unit includes: timing controller 22 and computer 21;

[0081] The timing controller 22 is electrically connected to the Nd:YAG laser 18 and the six-channel fiber spectrometer 19. The timing controller 22 is used to control the timing of the Nd:YAG laser 18 emitting the LIBS laser beam 14 and the spectral acquisition timing of the six-channel fiber spectrometer 19. Through precise timing control, the triggering of the LIBS laser beam 14 and the spectral acquisition are coordinated, avoiding timing errors during the data acquisition process and improving the real-time and accuracy of the detection.

[0082] The computer 21 is electrically connected to the timing controller 22 , the LPBF laser unit and the LPBF printing unit. The computer 21 is used to coordinate the LPBF laser unit and the LPBF printing unit to work together, and is used to receive spectrum data and analyze the LIBS spectrum 16 .

[0083] In addition, to adjust the optical path of the LIBS spectrum 16, the LIBS element detection unit also includes a reflector 17. The reflector 17 is arranged on the optical path between the beam splitter 15 and the LIBS spectrum focusing mirror 20, and is used to reflect the LIBS spectrum 16 to the LIBS spectrum focusing mirror 20. The position of the LIBS spectrum focusing mirror 20 can be flexibly set.

[0084] Example 3

[0085] A LIBS detection method for online monitoring of nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF, the method comprising: a printing method and a detection method;

[0086] Printing methods include:

[0087] The 3D printing model of the stainless steel component is input into the calculation control unit, which sends printing and detection control instructions to the LPBF laser unit and LIBS element detection unit;

[0088] The LPBF laser unit, according to the instructions of the calculation control unit, guides the LPBF laser beam 11 through the galvanometer 10 to scan and selectively melt the metal powder layer layer by layer, forming a stainless steel component stacked layer by layer;

[0089] Methods for performing layer-by-layer printing include:

[0090] The powder feeding piston 1 pushes the metal powder in the powder feeding chamber 2 upward, and the powder spreading scraper 3 evenly spreads the powder into the printing chamber 5 to form a powder layer;

[0091] The galvanometer 10 guides the LPBF laser beam 11 according to a preset scanning path to selectively melt the metal powder on the surface of the printed layer, causing it to solidify to form a layer of the printed component;

[0092] After each layer of printing is completed, the printing piston 4 is used to push the printing chamber 5 down one layer;

[0093] Repeat all the above steps until the stainless steel component is printed layer by layer.

[0094] Specifically, the three-dimensional model of the LPBF print is input into computer 21, which simultaneously transmits instructions to timing controller 22 and LPBF control box 23. The LPBF laser unit and LIBS element detection unit operate in parallel to print the first layer of the stainless steel component. The powder feed piston 1 pushes the powder upward, and the powder spreading scraper 3 evenly scrapes the stainless steel powder from the powder feed chamber 2 to the printing chamber 5. Under the control of LPBF control box 23, the LPBF continuous laser 12 begins to emit LPBF laser light. The LPBF laser light is transmitted through a 1064nm dichroic mirror and focused by galvanometer 10 into LPBF printing focused laser light 9, which heats and melts the powder material. Under the directional control of LPBF printing focused laser light 9 by galvanometer 10, selective heating and melting of the powder material is achieved, completing the printing of this layer of the stainless steel component.

[0095] After the first layer of the stainless steel component is printed, the print piston 4 pushes the print chamber 5 down one layer to reserve space for the second layer of powder. Then the powder feeding piston 1 pushes the powder upward, and the powder scraper 3 evenly spreads the stainless steel powder to the print chamber 5, providing a uniform powder layer for the next laser scanning or melting. Repeat the steps until the entire stainless steel component is printed.

[0096] Detection methods include:

[0097] During the printing process of each layer, the LIBS element detection unit uses the Nd:YAG laser 18 to emit the LIBS laser beam 14, which is guided and focused to the surface of the printed layer by the dichroic mirror 13, the beam splitter 15 and the galvanometer 10 to excite and generate plasma 7;

[0098] The LIBS spectrum 16 emitted by the plasma 7 is reflected by the galvanometer 10 and the beam splitter, and then guided by the focusing lens of the LIBS spectrum 16 to the six-channel fiber optic spectrometer 19 for collection; the six-channel fiber optic spectrometer 19 converts the spectral signal into an electrical signal and transmits it to the calculation control unit;

[0099] The calculation control unit performs real-time analysis on the collected LIBS spectrum 16 to detect the concentration distribution of N, H, and O elements, such as Figure 3 、 Figure 4 and Figure 5 shown.

[0100] While LPBF printing is in progress, the LIBS element detection unit, under the control of a timing controller 22, excites and collects LIBS spectra 16 at a frequency of 10 Hz. During each cycle, a LIBS laser beam 14 is reflected by a reflector 17 and a 1064 nm dichroic mirror before entering a galvanometer 10. Focused into a LIBS excitation focused laser 8, it excites plasma 7 on the surface of the stainless steel layer. The plasma 7 then emits a LIBS spectrum 16, which is reflected by the galvanometer 10 and the 1064 nm dichroic mirror, transmitted through a 532 nm beam splitter, and reflected by a reflector 17. The spectrum is collected by a LIBS spectrum focusing mirror 20 and directed to a six-channel fiber optic spectrometer 19. The six-channel fiber optic spectrometer 19 collects the spectrum 2 μm after the emission of the LIBS laser beam 14, using a 9 μs gate width, and transmits it to a computer 21 for processing.

[0101] In the description of this specification, the description with reference to the terms "one embodiment / method", "some embodiments / methods", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments / methods or examples. In addition, those skilled in the art may combine and combine different embodiments / methods or examples described in this specification and the features of different embodiments / methods or examples, unless they are contradictory.

[0102] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0103] It should be understood by those skilled in the art that the above embodiments are merely for the purpose of illustrating the present invention clearly, and are not intended to limit the scope of the present invention. For those skilled in the art, other changes or modifications may be made based on the above invention, and these changes or modifications are still within the scope of the present invention.

Claims

1. A LIBS detection device for online monitoring of nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF, characterized in that: include: LPBF printing unit, used for feeding and spreading metal powder and printing stainless steel samples layer by layer (6); LPBF laser unit, used to generate and control the laser beam required in the printing process, and selectively scan and melt the metal powder layer; A LIBS element detection unit, used for emitting a pulsed laser to ablate the stainless steel sample (6) printed layer by layer to generate plasma (7), and collecting a LIBS spectrum (16) emitted by the plasma (7); A calculation control unit is electrically connected to the LIBS element detection unit and the LPBF laser unit, and is used to control the emission time of the pulsed laser and the collection timing of the LIBS spectrum (16), and analyze the collected LIBS spectrum (16); The laser beams emitted by the LPBF laser unit and the LIBS element detection unit are both directed into the stainless steel sample (6) in the printing state in the LPBF printing unit.

2. A LIBS detection device for online monitoring of nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF according to claim 1, characterized in that: The LPBF printing unit comprises: a powder feeding area, a printing area and a powder spreading scraper (3), wherein metal powder is arranged in the powder feeding area, and a stainless steel sample (6) obtained by layer-by-layer printing is located in the printing area, and the powder spreading scraper (3) is arranged between the powder feeding area and the printing area, and is used to horizontally move the metal powder in the powder feeding area to the printing area and spread it evenly, and the laser beams emitted by the LPBF laser unit and the LIBS element detection unit are both projected into the stainless steel sample (6) in the printing state in the printing area.

3. A LIBS detection device for online monitoring of nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF according to claim 2, characterized in that: The powder feeding area comprises: a powder feeding chamber (2) and a powder feeding piston (1), the metal powder is arranged in the powder feeding chamber (2), the powder feeding piston (1) is arranged in the powder feeding chamber (2) and is located below the metal powder, and the powder feeding piston (1) pushes the metal powder to move upward; The printing area comprises: a printing chamber (5) and a printing piston (4); waste powder is arranged in the printing chamber (5); a stainless steel sample (6) in a printing state is placed on the waste powder; the printing piston (4) is arranged in the printing chamber (5) and is located below the waste powder; and the printing piston (4) pushes the waste powder downward.

4. A LIBS detection device for online monitoring of nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF according to claim 1, characterized in that: The LPBF laser unit comprises: a galvanometer (10), an LPBF continuous laser (12), a dichroic mirror (13) and an LPBF control box (23); The galvanometer (10) is arranged above the stainless steel sample (6); the LPBF laser beam (11) emitted by the LPBF continuous laser (12) is transmitted through the dichroic mirror (13) and is focused by the galvanometer (10) to form an LPBF printing focused laser (9); and the LPBF control box (23) is electrically connected to the LPBF continuous laser (12) and the galvanometer (10); The dichroic mirror (13) is used to transmit the LPBF laser beam (11) and reflect light of other wavelength bands, and the LPBF control box (23) is used to control the emission of the LPBF laser beam (11) and the scanning path of the galvanometer (10).

5. A LIBS detection device for online monitoring of nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF according to claim 4, characterized in that: The LIBS element detection unit comprises: a beam splitter (15), a Nd:YAG laser (18), a LIBS spectrum (16) focusing lens and a six-channel fiber optic spectrometer (19); The LIBS laser beam (14) emitted by the Nd:YAG laser (18) is reflected by a dichroic mirror (13) and a beam splitter (15), and is focused by the galvanometer (10) to form a LIBS excitation focused laser (8); the beam splitter (15) is used to reflect the LIBS laser beam (14) and transmit light of other wavelength bands; The LIBS spectrum (16) focusing lens is used to collect the LIBS spectrum (16) emitted by the plasma (7) excited by the LIBS excitation focusing laser (8) on the surface of the stainless steel sample (6), and guide the LIBS spectrum (16) to the six-channel fiber optic spectrometer (19); After being reflected by the galvanometer (10) and the dichroic mirror (13), the LIBS spectrum (16) is transmitted through the beam splitter (15) and enters the LIBS spectrum (16) focusing lens.

6. A LIBS detection device for online monitoring of nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF according to claim 5, characterized in that: The LPBF continuous laser (12) emits 1064nm laser light, and the Nd:YAG laser (18) emits 532nm pulsed laser light; The dichroic mirror (13) transmits 1064nm laser light and reflects 532nm laser light and visible light; the beam splitter (15) is a 532nm beam splitter; The optical axis of the dichroic mirror (13) and the optical axis of the beam splitter (15) form an angle of 45° with the propagation path of the laser beam.

7. A LIBS detection device for online monitoring of nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF according to claim 5, characterized in that: The calculation control unit comprises: a timing controller (22) and a computer (21); The timing controller (22) is electrically connected to the Nd:YAG laser (18) and the six-channel fiber optic spectrometer (19), and the timing controller (22) is used to control the timing of the Nd:YAG laser (18) emitting the LIBS laser beam (14) and the timing of spectrum collection of the six-channel fiber optic spectrometer (19); The computer (21) is electrically connected to the timing controller (22), the LPBF laser unit and the LPBF printing unit. The computer (21) is used to coordinate the LPBF laser unit and the LPBF printing unit to work together, and is used to receive spectrum data and analyze the LIBS spectrum (16).

8. The LIBS detection device for online monitoring of nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF according to claim 5, characterized in that: The LIBS element detection unit further comprises: a reflector (17), wherein the reflector (17) is arranged on an optical path between the beam splitter (15) and the LIBS spectrum focusing mirror (20), and the reflector (17) is used to reflect the LIBS spectrum (16) to the LIBS spectrum focusing mirror (20).

9. A LIBS detection method for online monitoring of nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF, characterized in that: Methods include: Printing method and detection method; The printing method comprises: The three-dimensional printing model of the stainless steel component is input into a computing control unit, and the computing control unit sends printing and detection control instructions to the LPBF laser unit and the LIBS element detection unit; The LPBF laser unit guides the LPBF laser beam (11) to scan and selectively melt the metal powder layer layer by layer through a galvanometer (10) according to the instruction of the computing control unit, so as to form a stainless steel component stacked layer by layer; The detection method comprises: During the printing process of each layer, the LIBS element detection unit uses a Nd:YAG laser (18) to emit a LIBS laser beam (14), guides the LIBS laser beam (14) to focus on the surface of the printed layer through a dichroic mirror (13), a beam splitter (15) and a galvanometer (10), and excites and generates plasma (7); The LIBS spectrum (16) emitted by the plasma (7) is reflected by the galvanometer (10) and the beam splitter, and then guided by the LIBS spectrum (16) focusing lens to a six-channel fiber optic spectrometer (19) for collection; the six-channel fiber optic spectrometer (19) converts the spectrum signal into an electrical signal and transmits it to a calculation control unit; The calculation control unit performs real-time analysis on the collected LIBS spectrum (16) to detect the concentration distribution of N, H and O elements.

10. The LIBS detection method for online monitoring of nitrogen, hydrogen and oxygen elements in stainless steel prepared by LPBF according to claim 9, characterized in that: Methods for performing layer-by-layer printing include: The powder feeding piston (1) is used to push the metal powder in the powder feeding chamber (2) upward, and the powder is evenly spread in the printing chamber (5) by the powder spreading scraper (3) to form a powder layer; The galvanometer (10) guides the LPBF laser beam (11) according to a preset scanning path to selectively melt the metal powder on the surface of the printing layer, so that the metal powder solidifies to form a layer of the printing component; After the printing of the layer is completed, the printing piston (4) is used to push the printing chamber (5) down one layer; Repeat all the above steps until the stainless steel component is printed layer by layer.

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