Additive manufacturing(AM)is a reliable technique for constructing highly complex metallic parts.Direct energy deposition(DED)is one of the most common technologies used for AM-printed metal alloys.However,issues such...Additive manufacturing(AM)is a reliable technique for constructing highly complex metallic parts.Direct energy deposition(DED)is one of the most common technologies used for AM-printed metal alloys.However,issues such as weak binding,poor accuracy,and rough surfaces still affect the final products.These limitations in the metal-feed DED process indicate that post-processing techniques are required to achieve high quality in terms of both mechanical properties and surface finish.Conventional contact-based post-processing methods have several drawbacks,including difficulties in accessing complex shapes,environmental impact,high time consumption and cost,and health risks for operators.To address these problems and improve surface quality,a laser polishing process has been proposed.By melting or ablating the material with a laser,the laser-polishing process enables the smoothing of the initial topography.It should be noted that there are currently no reviews focusing specifically on laser polishing as a surface treatment technology for the DED process.Therefore,this review presents a unique examination of the mechanisms and primary user-set parameters for both continuous wave(CW)and pulsed laser polishing.The objective is to demonstrate the capabilities of each process and the benefits of using them for the surfaces of DED metal parts.Additionally,existing knowledge and technology gaps are identified,and future research directions are discussed.展开更多
Surface defects introduced by conventional mechanical processing methods can induce irreversible damage and reduce the service life of optics applied in high-power lasers.Compared to mechanical processing,laser polish...Surface defects introduced by conventional mechanical processing methods can induce irreversible damage and reduce the service life of optics applied in high-power lasers.Compared to mechanical processing,laser polishing with moving beam spot is a noncontact processing method,which is able to form a defect-free surface.This work aims to explore the mechanism of forming a smooth,defect-free fused silica surface by high-power density laser polishing with coupled multiple beams.The underlying mechanisms of laser polishing was revealed by numerical simulations and the theoretical results were verified by experiments.The simulated polishing depth and machined surface morphology were in close agreement with the experimental results.To obtain the optimized polishing quality,the effects of laser polishing parameters(e.g.overlap rate,pulse width and polishing times)on the polishing quality were experimentally investigated.It was found that the processing efficiency of fused silica materials by carbon dioxide(CO2)laser polishing could reach 8.68 mm2 s−1,and the surface roughness(Ra)was better than 25 nm.Besides,the cracks on pristine fused silica surfaces introduced by initial grinding process were completely removed by laser polishing to achieve a defect-free surface.The maximum laser polishing rate can reach 3.88μm s−1,much higher than that of the traditional mechanical polishing methods.The rapid CO2 laser polishing can effectively achieve smooth,defect-free surface,which is of great significance to improve the surface quality of fused silica optics applied in high-power laser facilities.展开更多
Laser Powder Bed Fusion (LPBF) is an Additive Manufacturing technique, which allows production of highly complex solid metal parts with good mechanical properties, compared to conventionally manufactured parts. Nevert...Laser Powder Bed Fusion (LPBF) is an Additive Manufacturing technique, which allows production of highly complex solid metal parts with good mechanical properties, compared to conventionally manufactured parts. Nevertheless, the layer-by-layer fabrication process also offers several disadvantages, including a relatively high surface roughness depending on the shape of the component, its position and orientation during the fabrication process. This paper deals with investigations on the surface roughness reduction capability, and residual surface structures by laser polishing of LPBF AlSi10Mg parts under varying initial surface roughness in order to investigate the influence of the surface behavior and initial surface roughness to the achievable surface quality by laser polishing. Hereto test specimens with varying fabrication orientations regarding to the built platform are printed and further polished. Thereby the initial arithmetic roughness varies between 19.2 μm and 8.0 μm. It could be shown that the achievable surface roughness by laser polishing with continuous and pulsed laser radiation is increasing with rising initial roughness, but the relative roughness reduction is almost constant in the range of 95% - 97.5%. The analyzation of the residual roughness structures shows, that the main roughness differences is found in the middle and long structure wavelength regime, which are directly depending on the initial surface structures of 3D printing.展开更多
The selective laser melting(SLM)technique applied to high-entropy alloys(HEAs)has attracted considerable attention in recent years.However,its practical application has been restricted by poor surface quality.In this ...The selective laser melting(SLM)technique applied to high-entropy alloys(HEAs)has attracted considerable attention in recent years.However,its practical application has been restricted by poor surface quality.In this study,the capability of laser polishing on the rough surface of a Co-free HEA fabricated using SLM was examined.Results show that the initial SLM-manufactured(as-SLMed)surface of the Co-free HEA,with a roughness exceeding 3.0μm,could be refined to less than 0.5μm by laser polishing.Moreover,the microstructure,microhardness,and wear resistance of the laser-polished(LP-ed)zone were investigated.Results indicate that compared with the microhardness and wear resistance of the as-SLMed layer,those of the LP-ed layer decreased by 4%and 11%,respectively,because of the increase in grain size and reduction of the BCC phase.This study shows that laser polishing has an excellent application prospect in surface improvement of HEAs manufactured by SLM.展开更多
Laser polishing is widely employed to reduce the surface roughness of products with complex geometries.Traditional laser polishing techniques use a single high-power Gaussian beam to melt and smooth a thin layer of su...Laser polishing is widely employed to reduce the surface roughness of products with complex geometries.Traditional laser polishing techniques use a single high-power Gaussian beam to melt and smooth a thin layer of surface material.However,the reliance on high power lasers can present practical challenges such as minimizing surface evaporation or reducing overall cost.In this work,we combined two identical low-power laser beams with a spatial offset in between them to construct an elliptical beam.By changing the spatial offset,combined beams with different lengths along the major axis can be created.We observe over 20%improvement in line roughness reduction using this approach compared to a single Gaussian laser beam with the same total power.Additionally,both experiment and simulation results suggest such improvement is because this dual-laser set-up can create a longer molten pool compared to a single laser.展开更多
This paper proposes a scanner–stage synchronized approach emphasizing a novel control structure for the laser polishing of Inconel 718 components manufactured by selective laser melting in order to address increasing...This paper proposes a scanner–stage synchronized approach emphasizing a novel control structure for the laser polishing of Inconel 718 components manufactured by selective laser melting in order to address increasing demands for high surface quality in metal additive manufacturing.The proposed synchronized control system is composed of a motion decomposition module and an error synthesis module.The experimental results show that stitching errors can be avoided thanks to continuous motion during laser processing.Moreover,in comparison with the existing step-scan method,the processing efficiency of the proposed method is improved by 38.22%and the surface quality of the laser-polished area is significantly enhanced due to a more homogeneous distribution of the laser energy during the material phase change.The proposed synchronized system paves the way for high-speed,high-precision,and large-area laser material processing without stitching errors.展开更多
Laser polishing(LP)is considered an effective method for generating ultrasmooth surfaces owing to its precision,flexibility,and material compatibility.However,a lack of understanding of the evolution of surface topogr...Laser polishing(LP)is considered an effective method for generating ultrasmooth surfaces owing to its precision,flexibility,and material compatibility.However,a lack of understanding of the evolution of surface topography during LP significantly limits the achievable surface roughness in practice.In this work,for the first time,by employing optical time-stretch quantitative interferometry(OTS-QI),we recorded the entire evolution of surface topography during LP with nanosecond-level temporal resolution,providing insight into the mechanisms involved in the surface roughness evolution,such as the Marangoni effect and the formation mechanism of mid-frequency waviness(MFW).Assisted by numerical calculations,we reveal that a‘perfect polishing point’exists,i.e.,the optimal interaction time for LP at a specific laser power density,at which the surface roughness can be minimised without the formation of an MFW owing to the Marangoni effect and non-uniform removal.This OTS-QI system harnesses the rapid repetition rate of femtosecond lasers,achieving a remarkable measurement speed exceeding 100,000,000 times per second while preserving a measurement accuracy comparable to that of existing white light interferometers(WLIs),setting a new benchmark as the fastest recorded roughness measurement.In addition to LP,the proposed method can be applied for real-time and in situ monitoring of many machining scenarios involving highly dynamic phenomena.展开更多
Slicing and post-treatment of SiC crystals have been a significant challenge in the integrated circuit and microelectronics industry.To compete with wire-sawing and mechanical grinding technology,a promis-ing approach...Slicing and post-treatment of SiC crystals have been a significant challenge in the integrated circuit and microelectronics industry.To compete with wire-sawing and mechanical grinding technology,a promis-ing approach combining laser slicing and laser polishing technologies has been innovatively applied to increase utilization and decrease damage defects for single crystal 4H-SiC.Significant material utiliza-tion has been achieved in the hybrid laser processes,where material loss is reduced by 75%compared to that of conventional machining technologies.Without any special process control or additional treat-ment,an internally modified layer formed by laser slicing can easily separate the 4H-SiC crystals using an external force of about∼3.6 MPa.The modified layer has been characterized using a micro-Raman method to determine residual stress.The sliced surface exhibits a combination of smooth and coarse appearances around the fluvial morphology,with an average surface roughness of over S_(a) 0.89μm.An amorphous phase surrounds the SiC substrate,with two dimensions of lattice spacing,d=0.261 nm and d=0.265 nm,confirmed by high-resolution transmission electron microscopy(HRTEM).The creation of laser-induced periodic surface nanostructures in the laser-polished surface results in a flatter surface with an average roughness of less than S_(a) 0.22μm.Due to the extreme cooling rates and multiple thermal cy-cles,dissociation of Si-C bonding,and phase separation are identified on the laser-polished surface,which is much better than that of the machining surface.We anticipate that this approach will be applicable to other high-value crystals and will have promising viability in the aerospace and semiconductor industries.展开更多
The electromagnetic shielding film has drawn much attention due to its wide applications in the integrated circuit package,which demands a high surface quality of epoxy resin.However,gaseous Cu will splash and adhere ...The electromagnetic shielding film has drawn much attention due to its wide applications in the integrated circuit package,which demands a high surface quality of epoxy resin.However,gaseous Cu will splash and adhere to epoxy resin surface when the Cu layer in PCB receives enough energy in the process of laser cutting,which has a negative effect on the quality of the shielding film.Laser polishing technology can solve this problem and it can effectively improve the quality of epoxy resin surface.The paper studies the mechanism of Cu powder spraying on the compound surface by 355 nm ultraviolet（UV） laser,including the parameters of laser polishing process and the remains of Cu content on compound surface.The results show that minimal Cu content can be realized with a scanning speed of 700 mm/s,a laser frequency of 50 kHz and the distance between laser focus and product top surface of-1.3 mm.This result is important to obtain an epoxy resin surface with high quality.展开更多
Optimizing laser processes is historically challenging,requiring extensive and costly experimentation.To solve this issue,we apply Bayesian optimization for process parameter optimization to laser cutting,welding,and ...Optimizing laser processes is historically challenging,requiring extensive and costly experimentation.To solve this issue,we apply Bayesian optimization for process parameter optimization to laser cutting,welding,and polishing.We demonstrate how readily available Bayesian optimization frameworks enable efficient optimization of laser processes with only modest expert knowledge.Case studies on laser cutting,welding,and polishing highlight its adaptability to real-world manufacturing scenarios.Moreover,the examples emphasize that with suitable cost functions and boundaries an acceptable optimization result can be achieved after a reasonable number of experiments.展开更多
基金supported by National Key Research and Development Program of China(Grant No.2022YFB4600901).
文摘Additive manufacturing(AM)is a reliable technique for constructing highly complex metallic parts.Direct energy deposition(DED)is one of the most common technologies used for AM-printed metal alloys.However,issues such as weak binding,poor accuracy,and rough surfaces still affect the final products.These limitations in the metal-feed DED process indicate that post-processing techniques are required to achieve high quality in terms of both mechanical properties and surface finish.Conventional contact-based post-processing methods have several drawbacks,including difficulties in accessing complex shapes,environmental impact,high time consumption and cost,and health risks for operators.To address these problems and improve surface quality,a laser polishing process has been proposed.By melting or ablating the material with a laser,the laser-polishing process enables the smoothing of the initial topography.It should be noted that there are currently no reviews focusing specifically on laser polishing as a surface treatment technology for the DED process.Therefore,this review presents a unique examination of the mechanisms and primary user-set parameters for both continuous wave(CW)and pulsed laser polishing.The objective is to demonstrate the capabilities of each process and the benefits of using them for the surfaces of DED metal parts.Additionally,existing knowledge and technology gaps are identified,and future research directions are discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.51775147,51705105)Science Challenge Project(Grant No.TZ2016006-0503-01)+3 种基金Young Elite Scientists Sponsorship Program by CAST(Grant No.2018QNRC001)China Postdoctoral Science Foundation funded project(Grant Nos.2018T110288,2017M621260)Self-Planned Task(Grant Nos.SKLRS201718A,SKLRS201803B)of State Key Laboratory of Robotics and System(HIT)Fundamental Research Funds for the Central Universities(Grant No.HIT.NSRIF.2019053).
文摘Surface defects introduced by conventional mechanical processing methods can induce irreversible damage and reduce the service life of optics applied in high-power lasers.Compared to mechanical processing,laser polishing with moving beam spot is a noncontact processing method,which is able to form a defect-free surface.This work aims to explore the mechanism of forming a smooth,defect-free fused silica surface by high-power density laser polishing with coupled multiple beams.The underlying mechanisms of laser polishing was revealed by numerical simulations and the theoretical results were verified by experiments.The simulated polishing depth and machined surface morphology were in close agreement with the experimental results.To obtain the optimized polishing quality,the effects of laser polishing parameters(e.g.overlap rate,pulse width and polishing times)on the polishing quality were experimentally investigated.It was found that the processing efficiency of fused silica materials by carbon dioxide(CO2)laser polishing could reach 8.68 mm2 s−1,and the surface roughness(Ra)was better than 25 nm.Besides,the cracks on pristine fused silica surfaces introduced by initial grinding process were completely removed by laser polishing to achieve a defect-free surface.The maximum laser polishing rate can reach 3.88μm s−1,much higher than that of the traditional mechanical polishing methods.The rapid CO2 laser polishing can effectively achieve smooth,defect-free surface,which is of great significance to improve the surface quality of fused silica optics applied in high-power laser facilities.
文摘Laser Powder Bed Fusion (LPBF) is an Additive Manufacturing technique, which allows production of highly complex solid metal parts with good mechanical properties, compared to conventionally manufactured parts. Nevertheless, the layer-by-layer fabrication process also offers several disadvantages, including a relatively high surface roughness depending on the shape of the component, its position and orientation during the fabrication process. This paper deals with investigations on the surface roughness reduction capability, and residual surface structures by laser polishing of LPBF AlSi10Mg parts under varying initial surface roughness in order to investigate the influence of the surface behavior and initial surface roughness to the achievable surface quality by laser polishing. Hereto test specimens with varying fabrication orientations regarding to the built platform are printed and further polished. Thereby the initial arithmetic roughness varies between 19.2 μm and 8.0 μm. It could be shown that the achievable surface roughness by laser polishing with continuous and pulsed laser radiation is increasing with rising initial roughness, but the relative roughness reduction is almost constant in the range of 95% - 97.5%. The analyzation of the residual roughness structures shows, that the main roughness differences is found in the middle and long structure wavelength regime, which are directly depending on the initial surface structures of 3D printing.
基金supported by the Shenzhen Science and Technology Program,China(Grant No.GJHZ20220913143012022)the School-level Scientific Research Project of Shenzhen Institute of Technology,China(Grant No.2211017)+4 种基金the Natural Science Foundation of Guangdong Province,China(Grant No.2023A1515011641)the Key field Research Projects of Foshan City,China(Grant No.2120001009232)the Guangdong Huazhong University of Science and Technology Industrial Technology Research Institute,China,and Guangdong Provincial Key Laboratory of Manufacturing Equipment Digitization,China(Grant No.2020B1212060014)the Postdoctoral Science Foundation of China(Grant No.2022M710503)the Natural Science Foundation Commission of Chongqing,China(Grant No.CSTB2022NSCQ-BHX0029).
文摘The selective laser melting(SLM)technique applied to high-entropy alloys(HEAs)has attracted considerable attention in recent years.However,its practical application has been restricted by poor surface quality.In this study,the capability of laser polishing on the rough surface of a Co-free HEA fabricated using SLM was examined.Results show that the initial SLM-manufactured(as-SLMed)surface of the Co-free HEA,with a roughness exceeding 3.0μm,could be refined to less than 0.5μm by laser polishing.Moreover,the microstructure,microhardness,and wear resistance of the laser-polished(LP-ed)zone were investigated.Results indicate that compared with the microhardness and wear resistance of the as-SLMed layer,those of the LP-ed layer decreased by 4%and 11%,respectively,because of the increase in grain size and reduction of the BCC phase.This study shows that laser polishing has an excellent application prospect in surface improvement of HEAs manufactured by SLM.
基金This study was supported by Princeton University Eric and Wendy Schmidt Transformative Technology Fund.This simulation was funded by Comunidad de Madrid Project ADITIMAT-CM(S2018/NMT-4411)Universidad Politecnicade Madrid Research Grant(EST-PDI-19-A1JMBI-26-T4MNY9).The authors also want to thank Luc Deike for valuable discussions.The authors acknowledge the use of Princeton's Imaging and Analysis Center,which is partially supported by the Princeton Center for Complex Materials,a National Science Foundation(NSF)MRSEC program(DMR-1420541),for the SEM image acquisition.
文摘Laser polishing is widely employed to reduce the surface roughness of products with complex geometries.Traditional laser polishing techniques use a single high-power Gaussian beam to melt and smooth a thin layer of surface material.However,the reliance on high power lasers can present practical challenges such as minimizing surface evaporation or reducing overall cost.In this work,we combined two identical low-power laser beams with a spatial offset in between them to construct an elliptical beam.By changing the spatial offset,combined beams with different lengths along the major axis can be created.We observe over 20%improvement in line roughness reduction using this approach compared to a single Gaussian laser beam with the same total power.Additionally,both experiment and simulation results suggest such improvement is because this dual-laser set-up can create a longer molten pool compared to a single laser.
基金The authors would like to acknowledge support from the National Natural Science Foundation of China(51875313 and 51705013)the Open Foundation of the State Key Laboratory of Tribology&Institute of Manufacturing Engineering(SKLT2019C09).
文摘This paper proposes a scanner–stage synchronized approach emphasizing a novel control structure for the laser polishing of Inconel 718 components manufactured by selective laser melting in order to address increasing demands for high surface quality in metal additive manufacturing.The proposed synchronized control system is composed of a motion decomposition module and an error synthesis module.The experimental results show that stitching errors can be avoided thanks to continuous motion during laser processing.Moreover,in comparison with the existing step-scan method,the processing efficiency of the proposed method is improved by 38.22%and the surface quality of the laser-polished area is significantly enhanced due to a more homogeneous distribution of the laser energy during the material phase change.The proposed synchronized system paves the way for high-speed,high-precision,and large-area laser material processing without stitching errors.
基金supported by the National Natural Science Foundation of China(12374295,62075200)the National Key Research and Development Program of China(2023YFB4603803)+2 种基金The Fund of National Key Laboratory of Plasma Physics(6142A04230201)Fundamental Research Funds for the Central Universities(2042023kf0113)the Shenzhen Science and Technology Program(20JCYJ20220530140601003).
文摘Laser polishing(LP)is considered an effective method for generating ultrasmooth surfaces owing to its precision,flexibility,and material compatibility.However,a lack of understanding of the evolution of surface topography during LP significantly limits the achievable surface roughness in practice.In this work,for the first time,by employing optical time-stretch quantitative interferometry(OTS-QI),we recorded the entire evolution of surface topography during LP with nanosecond-level temporal resolution,providing insight into the mechanisms involved in the surface roughness evolution,such as the Marangoni effect and the formation mechanism of mid-frequency waviness(MFW).Assisted by numerical calculations,we reveal that a‘perfect polishing point’exists,i.e.,the optimal interaction time for LP at a specific laser power density,at which the surface roughness can be minimised without the formation of an MFW owing to the Marangoni effect and non-uniform removal.This OTS-QI system harnesses the rapid repetition rate of femtosecond lasers,achieving a remarkable measurement speed exceeding 100,000,000 times per second while preserving a measurement accuracy comparable to that of existing white light interferometers(WLIs),setting a new benchmark as the fastest recorded roughness measurement.In addition to LP,the proposed method can be applied for real-time and in situ monitoring of many machining scenarios involving highly dynamic phenomena.
基金supported by National Natural Science Foundation of China(No.62304249)a project funded by China Postdoctoral Science Foundation(No.2023M733704).
文摘Slicing and post-treatment of SiC crystals have been a significant challenge in the integrated circuit and microelectronics industry.To compete with wire-sawing and mechanical grinding technology,a promis-ing approach combining laser slicing and laser polishing technologies has been innovatively applied to increase utilization and decrease damage defects for single crystal 4H-SiC.Significant material utiliza-tion has been achieved in the hybrid laser processes,where material loss is reduced by 75%compared to that of conventional machining technologies.Without any special process control or additional treat-ment,an internally modified layer formed by laser slicing can easily separate the 4H-SiC crystals using an external force of about∼3.6 MPa.The modified layer has been characterized using a micro-Raman method to determine residual stress.The sliced surface exhibits a combination of smooth and coarse appearances around the fluvial morphology,with an average surface roughness of over S_(a) 0.89μm.An amorphous phase surrounds the SiC substrate,with two dimensions of lattice spacing,d=0.261 nm and d=0.265 nm,confirmed by high-resolution transmission electron microscopy(HRTEM).The creation of laser-induced periodic surface nanostructures in the laser-polished surface results in a flatter surface with an average roughness of less than S_(a) 0.22μm.Due to the extreme cooling rates and multiple thermal cy-cles,dissociation of Si-C bonding,and phase separation are identified on the laser-polished surface,which is much better than that of the machining surface.We anticipate that this approach will be applicable to other high-value crystals and will have promising viability in the aerospace and semiconductor industries.
基金Project supported by the National Natural Science Foundation of China(Nos.61574083,61434001)the National Basic Research Program(No.2015CB352100)+3 种基金the National Key Project of Science and Technology(No.2011ZX02403-002)the Special Fund for Agroscientic Research in the Public Interest of China(No 201303107)the support of the Independent Research Program of Tsinghua University(No.2014Z01006)Advanced Sensor and Integrated System Lab of Tsinghua University Graduate School at Shenzhen(No.ZDSYS20140509172959969)
文摘The electromagnetic shielding film has drawn much attention due to its wide applications in the integrated circuit package,which demands a high surface quality of epoxy resin.However,gaseous Cu will splash and adhere to epoxy resin surface when the Cu layer in PCB receives enough energy in the process of laser cutting,which has a negative effect on the quality of the shielding film.Laser polishing technology can solve this problem and it can effectively improve the quality of epoxy resin surface.The paper studies the mechanism of Cu powder spraying on the compound surface by 355 nm ultraviolet（UV） laser,including the parameters of laser polishing process and the remains of Cu content on compound surface.The results show that minimal Cu content can be realized with a scanning speed of 700 mm/s,a laser frequency of 50 kHz and the distance between laser focus and product top surface of-1.3 mm.This result is important to obtain an epoxy resin surface with high quality.
基金support of the projects within the InnovationsCampus Mobilität der Zukunft as well as for the sustainability support of the projects of the Exzellenzinitiative II.The authors would like to thank Precitec Optronik GmbH(Germany)for providing the OCT sensor Chrocodile2.The authors would like to thank Light Conversion(Lithuania)for providing the Carbide CB3-80 laser.The Laser beam source TruDisk8001(DFG object number:625617)was funded by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)-INST 41/990-1 FUGG.
文摘Optimizing laser processes is historically challenging,requiring extensive and costly experimentation.To solve this issue,we apply Bayesian optimization for process parameter optimization to laser cutting,welding,and polishing.We demonstrate how readily available Bayesian optimization frameworks enable efficient optimization of laser processes with only modest expert knowledge.Case studies on laser cutting,welding,and polishing highlight its adaptability to real-world manufacturing scenarios.Moreover,the examples emphasize that with suitable cost functions and boundaries an acceptable optimization result can be achieved after a reasonable number of experiments.
