Hybrid Laser Research Articles

Bio‐Inspired Hybrid Laser Direct Writing of Interfacial Adhesion for Universal Functional Coatings (Adv. Funct. Mater. 49/2024)

Bio‐Inspired Hybrid Laser Direct Writing of Interfacial Adhesion for Universal Functional Coatings (Adv. Funct. Mater. 49/2024)

Solar PV End-of-Life Waste Recycling: An Assessment of Mechanical Recycling Methods and Proposed Hybrid Laser and High Voltage Pulse Crushing Method

This research article investigates the recycling of end-of-life solar photovoltaic (PV) panels by analyzing various mechanical methods, including Crushing, High Voltage Pulse Crushing, Electrostatic Separation, Hot Knife Cutting, Water Jet Cutting, and Magnetic Separation. Each method’s effectiveness in extracting materials such as glass, silicon, metals (copper, aluminum, silver, tin, lead), and EVA was evaluated. The analysis reveals that no single method is entirely sufficient for comprehensive material recovery. Based on the data analysis, a new hypothetical hybrid method, Laser and High Voltage Pulse (L&HVP), is proposed, which integrates the precision of laser irradiation with the robustness of high voltage pulse crushing. The laser irradiation step would theoretically facilitate the removal of the ethylene-vinyl acetate (EVA) encapsulant, preparing the materials for subsequent separation. The high high-voltage pulse crushing would then selectively fragment and separate the remaining components, potentially enhancing material recovery efficiency while minimizing contamination. The proposed approach is grounded in the observed limitations of existing techniques. This method aims to offer a more comprehensive and sustainable solution for solar PV module recycling. Further research and experimentation are necessary to validate the effectiveness of the L&HVP method and its potential impact on the field of solar PV recycling.

Fabrication of micro holes with confined pitting corrosion by laser and electrochemical machining: pitting corrosion formation mechanisms and protection method

Laser and electrochemical hybrid machining (LECM) combines the advantages of high efficiency of laser processing and high surface quality of electrochemical machining and has been employed to process deep micro holes with high surface quality, high precision, and efficiency. However, surface pitting corrosion occurs around the entrance of the micro holes drilled by LECM, which deteriorates their surface quality and mechanical properties. This study revealed the mechanism of surface pitting corrosion formation mechanisms during LECM by characterizing surface micromorphology, chemical composition, microstructures, and surface stress. The difference between surface pitting corrosion area during LECM and the stray current corrosion during electrochemical machining was studied. Micro solid metal particles and inner microcavities were observed in micro pits. The depth of the micro pits was greater than that obtained using electrochemical machining. It has been concluded that in LECM, the surface pitting corrosion occurred owing to the enhanced stray current corrosion and the accumulation of solidified melt particles and cavitation microbubbles in the micro pits. Coaxial gas-assisted LECM was also proposed to restrict the surface pitting corrosion area. Experiments and simulations were conducted to verify the feasibility of minimizing the corrosion area using coaxial gas. The surface pitting corrosion area has been decreased by 85.1% at a coaxial gas pressure of 0.1MPa compared with that without coaxial gas assistance. Finally, the radial cooling holes with a diameter of 1.2mm and an aspect ratio of 125:1 in turbine blades with high surface quality were fabricated. This study provides a promising method to fabricate high-aspect-ratio micro-holes with high surface quality and high efficiency.

Laser Hybrid Welding—An Advanced Joining Technique for Welding of Thick Plates of Maraging Steel

Laser Hybrid Welding—An Advanced Joining Technique for Welding of Thick Plates of Maraging Steel

Microstructural evolution and mechanical properties of LDED Ti-6Al-4 V alloy polished with a hybrid laser polishing technique

Microstructural evolution and mechanical properties of LDED Ti-6Al-4 V alloy polished with a hybrid laser polishing technique

An 8-channel narrow linewidth multi-wavelength laser hybrid integrated by photonic wire bonding structures for DWDM systems

An 8-channel monolithically integrated narrow linewidth multi-wavelength laser array (NL-MLA) combined with the commercial 8 × 1 planar lightwave circuit (PLC) coupler by the photonic wire bonding (PWB) technique is demonstrated in this paper. A distributed feedback (DFB) laser with the high-reflection and anti-reflection coatings (HR-AR) and the tapered asymmetric corrugation-pitch-modulated (TACPM) grating structure is proposed. The TACPM grating is achieved by the reconstruction equivalent chirp (REC) technique, which is low-cost and of high wavelength accuracy. According to the numerical simulation results, under the unavoidable impact of the facet phase of the HR end, the TACPM DFB laser suppresses the longitudinal spatial hole burning (LSHB) effect significantly, while having better single-mode performance and control of wavelength compared with the conventional HR-AR DFB laser. An 8-channel HR-AR TACPM DFB NL-MLA is fabricated with the 0.8 nm wavelength spacing design. The hybrid integration between the 8-channel NL-MLA and the PLC chip is achieved using the PWB technique. Both good single-mode performance and accurate wavelength interval of 0.8 nm can be obtained when all channels work simultaneously. The laser linewidth is below 273.8 kHz with good uniformity, and the relative intensity noise is under −159.6 dB/Hz for each channel.

Fabrication of black metal surface for high solar energy absorption by femtosecond laser hybrid technology.

Metals are crucial for solar energy applications, but their highly reflective surfaces limit solar energy absorption. The difficulty in manufacturing an ideal light-absorbing structure limits the incorporation of anti-reflective characteristics in metals. In this study, a femtosecond laser method was introduced to form micro-nano structures in metals, enhancing absorption by the application of silver nanoparticles and resulting in solar absorption rates of 97.2%, 98.3%, and 98.9% for aluminum, titanium, and steel, respectively. The solar reflectance was reduced by 82.3%, 62.6%, and 79.2%, respectively, compared to bare metal. Photothermal conversion and deicing tests verified a more efficient photothermal conversion ability in the composite micro-nanostructure surface. Compared to bare metal, the structure has more than twice the solar absorption efficiency and improves the deicing efficiency by 132%. The resultant material exhibits high photothermal conversion and deicing efficiencies, enhancing its potential for solar energy applications, particularly in photothermal, photovoltaic, and thermal solar technologies.

The Influence of the Rolling Direction on the Mechanical Properties of the Al-Alloy EN AW-5454-D

A complementary characterisation of the Al-alloy EN AW-5454 was carried out, intended for obtaining the laser hybrid welding parameters of subassemblies in the automotive industry. The investigation included a microstructural examination and the determination of the alloy’s properties using several analytical methods (HV5 hardness measurement, tensile test, Charpy impact toughness, fracture mechanics analysis). Samples were prepared in the longitudinal and transverse directions of a cold-rolled sheet of EN AW-5454 with thicknesses of 3.5 mm and 4 mm. The measured hardness on the thinner sheet was 5% higher than on the thicker sheet. The tensile and yield strength were nominal, while the elongations were smaller by 2.2–3.2% for the longitudinal samples and by 2.7–13.7% for the transverse samples. The smaller deviations from the nominal values are for the thinner sheet metal. A precise topographical analysis showed the brittle fractures of the samples. The Charpy impact toughness results on the thicker plate showed a 20% greater work needed to break it in the longitudinal direction than in the transverse direction. With the thinner sheet metal, 40% greater work was needed. SEM (scanning electron microscope) analysis has shown that the intermetallic Al6(Mn,Fe) particles in the longitudinal samples were mostly intact, with evidence of tough areas on the upper part of the fracture, indicating a better toughness than the specimens in the transverse direction. More crushed intermetallic particles were observed at the fractures of the transverse samples, and their distribution appeared to be more oriented in the direction of rolling. Fracture mechanics SENB (single edge notch bending) tests and their analysis showed that the resistance of the material to crack propagation in the longitudinal sample was about 50% greater than that in the transverse sample. SEM analysis of the fractures showed that the state of the intermetallic particles in the fracture mechanics testing and the fracture mechanism differed from the one in the Charpy fractures.

Review and Analysis of Modern Laser Beam Welding Processes.

Laser beam welding is the most modern and promising process for the automatic or robotized welding of structures of the highest Execution Class, EXC3-4, which are made of a variety of weldable structural materials, mainly steel, titanium, and nickel alloys, but also a limited range of aluminum, magnesium, and copper alloys, reactive materials, and even thermoplastics. This paper presents a systematic review and analysis of the author's research results, research articles, industrial catalogs, technical notes, etc., regarding laser beam welding (LBW) and laser hybrid welding (LHW) processes. Examples of industrial applications of the melt-in-mode and keyhole-mode laser welding techniques for low-alloy and high-alloy steel joints are analyzed. The influence of basic LBW and LHW parameters on the quality of welded joints proves that the laser beam power, welding speed, and Gas Metal Arc (GMA) welding current firmly decide the quality of welded joints. A brief review of the artificial intelligence (AI)-supported online quality-monitoring systems for LBW and LHW processes indicates the decisive influence on the quality control of welded joints.

The energy synergistic mechanism of coaxial heterogeneous-wavelength hybrid laser beam and its effect on welding molten pool dynamics for aluminum alloy

The coaxial heterogeneous-wavelength hybrid laser beam (HW-HLB) heat source featuring a “Gauss + Flat top” energy distribution, which integrates the 1080 nm and 915 nm laser beam, was employed in this paper to achieve excellent stability in the welding of aluminum alloy. The interaction mechanism between aluminum alloy and laser beams with different wavelengths was taken as a point cut to explore the synergistic enhancement mechanism of coaxial HW-HLB . A thermal-fluid coupling model for HW-HLB welding, considering the synergistic effect of dual lasers, was established according to the welding experiment results. The influence of fiber laser power (PF) and diode laser power (PD) on the molten pool flow behavior during welding process was investigated. The dynamic of the molten pool and the maintenance mechanism of the keyhole were elucidated through in-situ monitoring experiments and thermal-flow simulations. The results indicated that, in contrast to the single fiber laser beam (FLB), the power density of HW-HLB presents a significant increase, which results in the “avalanche-like” augmentation of the plasma plume, as well as deeper depth of the keyhole. The energy synergistic enhancement effect of coaxial HW-HLB with PF=2800 W and PD=2500 W performs stronger and thorough changes in the morphology and flow behavior of the molten pool. The introduction of 915 nm laser beam improves the multi-reflection behavior in the inner keyhole. The findings of our research provide a theoretical framework for improving the stability of the laser weld molten pool and the quality of welds in aluminum alloys through the implementation of HW-HLB.

A comparative study for demonstrating the effect of the assist gas and E-field on hole generation characteristics induced by femtosecond laser layered ring hole-cutting of magnesium alloy AZ91D sheets

The widely-used magnesium alloy AZ91D is light-weight and energy-saving with good castability and mechanical performance. The traditional machining way for magnesium and its alloys is the high-speed mechanical contact cutting, which usually leads to uncontrollable intense ignition with some notable heat-induced machining defects. However, it has been rarely reported that the non-contact precision laser machining is used for cutting the magnesium and its alloys. The problems such as the local heat effect, the heat-induced defects and the local ignition as well as the vapor-plasma plume usually encountered during laser machining of magnesium and its alloys. Hence, in this study, a hybrid laser cutting way of femtosecond laser layered ring hole-cutting using the assist gas and E-field is reported to machine micro holes in the AZ91D material. The effect of the lateral E-field and assist gas on the hole formation characteristics was demonstrated for femtosecond laser cutting of the AZ91D sheets. It was indicated that the use of the lateral E-field and assist gas suppressed the ignition as well as the vapor-plasma plume. The hole depth was increased by the external assistance used especially the lateral nitrogen blowing. The hole wall formation quality was improved by using the lateral E-field and compressed air blowing, while it got poorer if using the lateral nitrogen blowing. The ignition-induced carbonization was effectively suppressed by the assist gas used. The hole depth, microstructure and micro hardness were improved by using the lateral E-field and assist gas.

Bio‐Inspired Hybrid Laser Direct Writing of Interfacial Adhesion for Universal Functional Coatings

AbstractEnhancing interfacial adhesion between functional coatings and target surfaces facilitates long‐term stable service by mitigating interferences of mechanical mismatches. Design of mechanical interlocks affords an effective strategy to strengthen the interfacial bonding with durability and compatibility, but the in‐depth investigations are still lacked. Herein, a gecko‐inspired hierarchical strategy realized by hybrid laser direct writing is proposed, which incorporates an armored frame scale for surface protection and a riveted anchor scale for interlocks. Such dual‐scale configurations endow the functional coatings with the stronger adhesion to the targets than the pristine and mono‐scale cases, resulting in 2 orders of magnitude enhancement resistant to tape peeling tests. Utilizing this scheme, a laser‐induced integrated deicing system is in situ manufactured on thermoplastics, primarily comprising superhydrophobic structures, carbon‐based sensors as well as adhesive copper (Cu) interconnects and heaters, where Cu‐based devices exhibit superior resistance to water impacts and stress fatigue. Interfacing with signal processing modules, such an all‐in‐one system demonstrates real‐time temperature monitoring and high efficiency in deicing (4.24 folds faster than the control group). The facile route for intensified adhesion holds promise in the interfaces within advanced equipment and under harsh scenarios.

Hybrid integrated GaSb/Si3N4 narrow linewidth (<50 kHz) distributed Bragg reflector laser

A narrow linewidth hybrid integrated distributed Bragg reflector (DBR) laser platform operating at 2 μm wavelength region is demonstrated. The laser architecture comprises AlGaInAsSb/GaSb type-I quantum well reflective semiconductor optical amplifiers butt-coupled to a Si3N4 photonic integrated circuit (PIC), incorporating a narrow-band DBR. The DBR is realized with a long spiral-shaped waveguide structure with periodic circular posts placed adjacent to the waveguide. At room temperature operating conditions, the laser exhibits a maximum continuous wave output power of more than 17 mW for emission near 2 μm. Linewidth properties are analyzed with a heterodyne measurement technique, involving the mixing of the laser signal with a frequency comb phase-locked to an ultra-stable laser. The hybrid laser exhibits a narrow linewidth of ∼8 kHz in 1 ms timescale and ∼50 kHz in 10 ms timescale.

Investigations of the hybrid laser polishing and high-temperature tribological properties of the 316L stainless steel formed by selective laser melting

In this study, the rough surfaces of additive manufactured parts were polished using an innovative combined treatment of continuous wave (CW) laser and inclined femtosecond (fs) laser techniques. The high-temperature friction and wear performances of the initial surface and the polished surface were investigated. The results indicate that the surface roughness was reduced to 0.21 µm and a fine-grained layer of approximately 25 µm was generated through CW-fs laser polishing. The coefficient of friction and wear volume of the CW-fs laser polished surface showed the most significant reductions of 52.2 % and 88.3 %, respectively, compared to those of initial surface under high-temperature conditions.

Amphibious Hybrid Laser Tweezers for Fluid and Solid Domains.

Optical trapping is a potent tool for achieving precise and noninvasive manipulation of small objects in a vacuum and liquids. However, due to the substantial disparity between optical forces and interfacial adhesion, target objects should be suspended in fluid environments, rendering solid contact surfaces a restricted area for conventional optical tweezers. In this work, by relying on a single continuous wave (CW) laser, we demonstrate an optical manipulation system applicable for both fluid and solid domains, namely, amphibious hybrid laser tweezers. The key to our system lies in modulating the intensity of the CW laser with duration shorter than the dynamic thermal equilibrium time within objects, wherein strong thermal gradient forces with ∼6 orders of magnitude higher than the forces in optical tweezers are produced, enabling moving and trapping micro/nano-objects on solid interfaces. Thereby, CW laser-based optical tweezers and pulsed laser-based photothermal shock tweezers are seamlessly fused with the advantages of cost-effectiveness and simplicity. Our concept breaks the stereotype that CW lasers are limited to generating tiny forces and instead achieve ultrawide force generation spanning from femto-newtons (10-15 N) to (10-6 N). Our work expands the horizon of optical manipulation by seamlessly bridging its applications in fluid and solid environments and holds promise for inspiring optical manipulation techniques to perform more challenging tasks, which may unearth application scenarios in diverse fields such as fundamental physical research, nanofabrication, micro/nanorobotics, biomedicine, and cytology.

An in-situ hybrid laser-induced integrated sensor system with antioxidative copper

Integration of sensors with engineering thermoplastics allows to track their health and surrounding stimuli. As one of vital backbones to construct sensor systems, copper (Cu) is highly conductive and cost-effective, yet tends to easily oxidize during and after processing. Herein, an in-situ integrated sensor system on engineering thermoplastics via hybrid laser direct writing is proposed, which primarily consists of laser-passivated functional Cu interconnects and laser-induced carbon-based sensors. Through a one-step photothermal treatment, the resulting functional Cu interconnects after reductive sintering and passivation are capable of resisting long-term oxidation failure at high temperatures (up to 170 °C) without additional encapsulations. Interfacing with signal processing units, such an all-in-one system is applied for long-term and real-time temperature monitoring. This integrated sensor system with facile laser manufacturing strategies holds potentials for health monitoring and fault diagnosis of advanced equipment such as aircrafts, automobiles, high-speed trains, and medical devices.

Combining Ultrafast Laser Texturing and Laser Hardening to Enhance Surface Durability by Improving Hardness and Wear Performance

Aluminum alloy 7075 is utilized widely across marine, aerospace, and automotive sectors. However, its surface wear resistance has hindered its application in certain tribological environments. Addressing this challenge, the current study examines a hybrid laser method to increase surface wear resistance by combining two techniques: ultrafast laser texturing and laser‐based surface hardening. Ultrafast laser processing is conducted using 3 W laser power, 100 kHz pulse repetition rate, 4 mm s−1 scanning speed, and three different scan patterns. After the texturing operation, laser‐based surface hardening is then performed on these textures using a continuous wave laser. The laser heat treatment is conducted using laser powers of 400 and 500 W with three different scan speeds of 1, 2, and 3 mm s−1. Microhardness evaluations show a notable increase in hardness, with the hardest sample exhibiting a 17.8% increase compared to the pristine sample. The laser‐textured and laser heat‐treated samples exhibit a significant reduction in the average coefficient of friction and wear volumes compared to samples that were laser‐textured but not laser heat‐treated. The investigated laser processing strategy offers a promising approach for surface modification, enhancing both mechanical properties and wear resistance of aluminum alloy 7075 surfaces.

Stabilising mechanism of cathode jet and droplet transfer in hybrid-laser–GMAW-based directed energy deposition of titanium alloy

ABSTRACT A hybrid laser–GMAW-based directed energy deposition (DED) was developed to stabilise the cathode jet and droplet transfer in DED of Ti alloy. High-speed photography, spectroscopic diagnostic, theoretical calculation, and numerical simulation were employed to investigate the stabilising mechanisms. At a high laser energy density, the highest temperature of the molten pool was located in the laser-irradiated zone, generating a stable cathode jet. Ti atoms easily ionised into Ti ions at high temperatures (>8200 K); therefore, the cathode jet was primarily composed of Ti ions. The laser-induced metal vapour attracted and contracted the arc, resulting in an increase in the arc temperature, and strong evaporation near the wire during the peak-current stage. Therefore, the distribution areas of Ti I and Ti II were enlarged. Introducing the laser inhibited the obstructive effect of the cathode jet on the droplet, thereby enhancing the stability of droplet transfer.

Synthesis of an Ultra-high Hardness Nanostructured AlSi10Mg Alloy via A Hybrid Laser Powder Bed Fusion/High-Pressure Torsion Approach

The hybrid combination of laser powder bed fusion (L-PBF) and high-pressure torsion, respectively an additive manufacturing (AM) and severe plastic deformation (SPD) has recently emerged as an important field of study due to the ability to produce novel nanostructured metals/alloys with simultaneous enhancements in mechanical (hardness, yield and tensile strengths) and functional (corrosion and wear) performances. Pioneering studies on the hybrid L-PBF/HPT approach was focused on 316L stainless steel (316L SS) and AlCuMg alloys due to their widespread engineering applications. AlSi10Mg, an alloy widely used in the automotive industry is expected to benefit from this hybrid combination but has not been investigated before. Thus, this study aims to investigate the microstructural features and hardness of the nanostructured AlSi10Mg attained by the hybrid L-PBF/HPT technique via transmission electron microscopy (TEM) and Vickers microhardness (HV) measurements, respectively. The results showed novel microstructures, including nano-scale grain sizes (< 200 nm), nano-sized Mg2Si precipitates (~200 nm), and dense dislocation networks. The average hardness value was determined as 230 ± 20 HV, homogeneously distributed throughout the disk surface as indicated by the low deviation (error bar). The microstructures of L-PBF/HPT-synthesised AlSi10Mg are different and significantly refined than conventionally cast AlSi10Mg, which contributed to the two- to four-fold hardness (typical HV values of as-cast AlSi10Mg ranges from 60 – 68 HV) increase via grain boundary and dislocation strengthening mechanisms.

Fiber laser irradiation in chemical solution for micro fabrication: Mechanisms and applications

The laser and electrochemical hybrid machining (LECM) could realize high-efficient and quality processing of difficult-to-cut materials and has become a research topic in microfabrication. However, it was difficult to ensure the stability and efficiency of laser transmission in chemical solutions, and an external voltage and auxiliary cathode should be added. In the present study, a novel fiber laser irradiation in chemical solution (LICS) has been proposed to process microstructures. The surface microstructures and chemical composition of the surfaces processed by LICS, laser irradiation in the ultrapure water, and electrochemical machining were compared. In LICS the materials were removed by laser processing and the following high-temperature gradient induced electrochemical dissolution. The high temperature gradient induced electrochemical dissolution could enhance the MRR and improve the surface quality. LICS can be regarded as a novel LECM process. The machining efficiency of LICS had been improved by 46.2 % compared with that laser irradiation in the ultrapure water, and the proportion of laser-induced electrochemical dissolution was 31.6 % in the LICS process. Further, the effects of laser power, chemical solution concentration, and optical fiber end movement control on the processing of micro grooves were explored, considering the dimension, MRR, and surface roughness. A front gap of smaller than 0.8 mm between the optical fiber end and workpiece was recommended during LICS. The repeated feeding of optical fiber was proposed to improve the depth-to-width ratio of the micro grooves fabricated by LICS. Finally, LICS was used to process microstructures with the controlled profiles on the nickel-based superalloy and titanium alloy workpieces without a recast layer, which holds great potential in surface microfabrication and texturing.