Laser Scanning Speed Research Articles

Temporal airy pulses efficiency in thin glass dicing

Abstract Ultrashort pulse laser sources are useful tools for micro- and nano-processing large band gap dielectric materials. One of the biggest advantages of these pulses is the possibility to reach high intensity peaks that promote absorption even in materials transparent to the laser wavelength. In addition, if the pulse temporal distribution is modified, energy absorption enables the ablation of small diameter holes with large depths. In this work, we present preliminary results that implement three types of pulses as precursors for glass dicing: Bandwidth-limited (30 fs at 785 nm), positively, and negatively dispersed Temporal Airy Pulses (TAP). The material of choice was 170 μm thick soda-lime glass, inscribed at 1 kHz repetition rate in tight (50× objective) and loose (20× objective) focusing conditions for different laser energies and scanning speeds. After laser processing, the glass was diced by mechanical stress, with a home built four-point bending stage. We analyzed the quality of the scribed lines at the surface and in cross-section after breaking, as well as the necessary breaking force for all three types of laser pulses. We report that positive TAP produced a neat, flat-cut edge on the glass samples compared with the other implemented pulses.

Atmosphere Effects in Laser Powder Bed Fusion: A Review

The use of components fabricated by laser powder bed fusion (LPBF) requires the development of processing parameters that can produce high-quality material. Manipulating the most commonly identified critical build parameters (e.g., laser power, laser scan speed, and layer thickness) on LPBF equipment can generate acceptable parts for established materials and moderately intricate part geometries. The need to fabricate increasingly complex parts from unique materials drives the limited research into LPBF process control using underutilized parameters, such as atmosphere composition and pressure. As presented in this review, manipulating atmosphere composition and pressure in laser beam welding has been shown to expand processing windows and produce higher-quality welds. The similarities between laser beam welding and laser-based AM processes suggest that this atmosphere control research could be effectively adapted for LPBF, an area that has not been widely explored. Tailoring this research for LPBF has significant potential to reveal novel processing regimes. This review presents the current state of the art in atmosphere research for laser beam welding and LPBF, with a focus on studies exploring cover gas composition and pressure, and concludes with an outlook on future LPBF atmosphere control systems.

Spatter detection and tracking in high-speed video observations of laser powder bed fusion

Purpose In laser powder bed fusion (L-PBF) additive manufacturing, spatter particles are ejected from the melt pool and can be detrimental to material performance and powder recycling. Quantifying spatter generation with respect to processing conditions is a step toward mitigating spatter and better understanding the phenomenon. This paper reveals process insights of spatter phenomena by automatically annotating spatter particles in high-speed video observations using machine learning. Design/methodology/approach A high-speed camera was used to observe the L-PBF process while varying laser power, laser scan speed and scan strategy on a constant geometry on an EOSM290 using Ti-6Al-4V powder. Two separate convolutional neural networks were trained to segment and track spatter particles in captured high-speed videos for spatter characterization. Findings Spatter generation and ejection angle significantly differ between keyhole and conduction mode melting. High laser powers lead to large ejections at the beginning of scan lines. Slow and fast build rates produce more spatter than moderate build rates at constant energy density. Scan strategies with more scan vectors lead to more spatter. The presence of powder significantly increases the amount of spatter generated during the process. Originality/value With the ability to automatically annotate a large volume of high-speed video data sets with high accuracy, an experimental design of observed parameter changes reveals quantitively stark changes in spatter morphology that can aid process development to mitigate spatter occurrence and impacts on material performance.

Investigating Melt Pool Dimensions in Laser Powder Bed Fusion of Nitinol: An Analytical Approach

Nitinol (NiTi) has gained popularity across various industries due to its shape memory and superelastic properties. Recently, additive manufacturing (AM) has been increasingly utilized to produce NiTi components. This study focuses on single‐track nitinol samples fabricated via powder bed fusion using laser beam (PBF‐LB). Investigating the effects of laser power and scanning speed on melt pool dimensions reveals that melt pool width increases linearly with laser power and decreases logarithmically with scanning speed. However, melt pool depth exhibits outliers that deviate from these trends. Three analytical models are evaluated to predict melt pool dimensions, generally aligning with experimental trends. Notably, the Eagar–Tsai model delivers the most accurate predictions for melt pool width, with a mean absolute error of less than 10%, while the Gladush–Smurov model is more reliable for melt pool depth predictions, showing a mean absolute error under 20%. In contrast, the Rosenthal equation yields less reliable results for both dimensions. This suggests that a combined approach utilizing the strengths of both the Eagar–Tsai and Gladush–Smurov models may provide the most accurate predictions for the melt pool profile of NiTi in PBF‐LB.

Effect of Processing Parameters on Recrystallization During Hot Isostatic Pressing of Stellite-6 Fabricated Using Laser Powder Bed Fusion Technique

Crack-free Stellite-6 alloy was fabricated using the laser powder bed fusion technique equipped with a heating module as the first attempt. Single tracks were printed with a build plate heated to 400 °C to identify the processing window. Based on the melt pool dimensions, two combinations (sample A: 300 W/750 mm/s and sample B: 275 W/1000 mm/s) were identified to print the cubes. The as-printed microstructure comprised FCC-Co dendrites with M7C3 in the interdendritic region. W-rich M6C particles were found in the overlapping regions between the melt pools, matching the Scheil simulations. However, gas pores were observed due to the higher nitrogen and oxygen content of the feedstock requiring hot isostatic pressing (HIP) at 1250 °C and 150 MPa for 2 h. Sample A was partially recrystallized with slightly coarsened M7C3, while sample B underwent complete recrystallization followed by grain growth along with higher coarsening of the M7C3 after HIP. The varying recrystallization behavior can be attributed to the difference in residual stresses and grain aspect ratio in the as-built condition dictated by laser power and scanning speed. The microhardness after HIP was slightly higher than its wrought counterpart, indicating no severe impact of post-processing on the properties of Stellite-6 alloy.

Optimisation of laser surface ablation of alumina/GO coating on AZ31D magnesium alloy using Cuckoo Search Algorithm method

ABSTRACT Graphene oxide (GO) and alumina (Al2O3) work in concert to give magnesium alloys advantageous surface qualities and protection from adverse environments. This paper aims to investigate the effect of laser surface treatment on plasma sprayed alumina-graphene oxide (GO) coating on AZ31D magnesium alloy. Key ablation quality responses; HAZ width, surface roughness and ablation rate were correlated with laser parameters using the Response Surface Methodology and optimised using the metaheuristic Cuckoo Search Algorithm Method. Laser power significantly influenced all ablation characteristics of the composite coating. The addition of 1.5 wt% GO in the alumina coating caused a significant reduction in HAZ width (43.32%), surface roughness (25.11%) and ablation rate (76.58%) when treated with optimal combinations of laser power (8 W), scanning speed (950 mm/s) and frequency (78.2 kHz). The surface quality was characterised by smooth textures, and resolidified splats along with deep pits when ablated with lower and intermediate power whereas surfaces ablated with higher power showed debonded splats with peripheral surface destruction. While a prominent 2D peak at 16 W confirmed the presence of GO layers during high-power laser contacts, the ID/IG ratio below unity across all specimens indicated minimal defect concentrations.

Comprehensive study on statistical methods for optimization of process parameters and material properties of AlSi10Mg in laser powder bed fusion

This study provides a systematic investigation of the effects of process parameters and heat treatments on the material properties of AlSi10Mg, produced by laser powder bed fusion (L-PBF). Using a central composite design (CCD) with 106 test specimens (49 cubes, 57 tensile), the samples were studied for key properties: density (up to 99.96%), hardness (up to 154.6 HV1), surface roughness (as low as 1.9 Ra), tensile strength (up to 487.5 MPa), and elongation at break (up to 16.6%). Statistical analysis (ANOVA) identified laser power and scanning speed as the most influential parameters on these properties. Additionally, heat treatment was shown to reduce hardness and tensile strength but increase elongation at break, demonstrating the ability to modify mechanical properties based on the desired outcome. Process parameter optimization yielded properties comparable to some of the highest reported values for AlSi10Mg in the literature. The study also discusses the transferability and reproducibility of L-PBF results across different machines, highlighting challenges related to machine-to-machine variations, lack of calibration and standardization and parameter consistency. The results demonstrate the potential of L-PBF to produce AlSi10Mg parts with tailored properties for industrial applications.

Highly Productive Laser Annealing Manufacturing Method Using Continuous Blue WBC (Wavelength Beam Combining) Technique

Blue laser annealing can be used to obtain a high-mobility thin-film transistor (TFT) through a laser annealing (i.e., LTPS: low-temperature Poly-Si) process. However, the laser annealing process’s low productivity (as well as high cost) is an issue because the high output power of blue lasers still needs to be addressed. Therefore, productivity can be improved if blue laser energy is efficiently supplied during the laser annealing process using a continuous wave laser instead of a conventional pulsed excimer laser. We developed a blue laser light source (440 ± 10 nm) using the wavelength beam combining (WBC) method, which can achieve a laser power density of 73.7 kW/cm2. In this semiconductor laser, when the power was increased s by 2.9 times, the laser scanning speed was increased by 5.0 times, achieving twice the productivity of conventional lasers. After laser annealing, the size of the crystal grains varied between 2 and 15 μm, resulting in a crystallization rate of 100% by Raman scattering rsult and low resistivity of 0.04 Ωcm. This increase in production capacity is not an arithmetic increase with increased power but a geometric production progression.

Investigation of laser sintering process parameters for anode foils in aluminium electrolytic capacitors considering temperature distribution

Abstract The anode foil is a critical component of aluminium electrolytic capacitors, with its performance directly impacting the overall quality of the capacitors. Currently, sintered anode foil with excellent bending resistance and high specific capacitance is considered an ideal material for capacitor manufacturing; however, research on its optimal sintering parameters remains insufficient. In this study, a three-dimensional temperature field model is developed within the Comsol Multiphysics (6.0) environment, accounting for the temperature dependence of aluminium. By varying laser power and scanning speed, the temperature distribution along the laser scanning trajectory is determined, facilitating the identification of optimal process parameters for laser sintering anode foils in electrolytic capacitors. Subsequent laser sintering experiments validate the accuracy of these parameters. The findings indicate that the peak temperature of the molten pool rises with increased laser power and decreased scanning speed. The optimal process parameters for laser sintering anode foils in electrolytic capacitors are a powder layer thickness of 50 µm, a laser power of 140 W, and a scanning speed of 0.05 m/s. The specific capacitance of laser-sintered anode foil, formed at voltages of 375 V and 520 V, ranges from 0.847 to 1.157 μF/cm² and 0.717 to 0.935 μF/cm², respectively, when the particle size is between 3 and 4 μm. A specific capacitance of 0.733 μF/cm² can be achieved, which meets the performance requirements for aluminium electrolytic capacitors.

Additive manufacturing of Fe–Mn–Al–C lightweight steel by laser powder bed fusion: The role of laser scanning speed on forming quality, microstructure and properties

The Fe–Mn–Al–C lightweight steels have attracted great attention in the military, aerospace, and automotive industries due to their high strength and lightweight design. Nevertheless, the excessive Mn and Al inclusions have led to poor formability and processability, which brings challenges to the manufacture of large size complex structural parts. In this study, the lightweight steel with a composition of Fe–Mn–Al–C was prepared by laser powder bed fusion for the first time, aimed at investigating the effects of laser scanning speed. The results show that different laser scanning speeds have significant effects on the process sensitivity of lightweight steel, and too low or too high laser scanning speeds may lead to suboptimal sample quality, increased porosity and surface roughness. At a scanning speed of 800 mm/s, the optimal conditions for the lowest porosity (0.03%) and surface roughness (Sa = 3.34 μm) are achieved, resulting in the highest quality of the formed products. Furthermore, an increase in scanning speed results in a reduction in grain size and an enhancement of dislocation strength. When the scanning speed is 800 mm/s, the significant enrichment of Ni–Mn phase helps to enhance the pinning ability of dislocations, while the precipitation of nanoscale small and dense κ-carbide optimizes the Orowan strengthening effect. As a result, dislocation movement is effectively impeded, leading to superior comprehensive mechanical properties of exceptional strength-plasticity matched with a tensile strength, yield strength, and elongation after fracture of 1125.2 MPa, 1019.8 MPa, and 41.9%, respectively.

Optimizing laser cladding process parameters for transformation-induced plasticity FeMnCoCr high entropy alloy: A multi-objective approach

A multi-objective optimization approach utilizing the response surface method (RSM) is proposed to determine the optimal processing parameters for laser cladding of Fe50Mn30Co10Cr10 coating. In this paper, a single-variable control method was employed to adjust the laser cladding parameters, and preliminary experiments were conducted to establish the optimization range for the RSM laser cladding parameters. A mathematical prediction model of input processing parameters (laser power, scanning speed and powder feed speed) and output response (dilution rate, W/H, microhardness and porosity) was established by the response surface method. The results indicated that both the dilution rate and microhardness had a positive correlation with laser power and scanning speed, while they were negatively correlated with the powder feed rate. The scanning speed is the most significant factor influencing the porosity of the coating, followed by the powder feed rate. The optimal processing parameters were identified as follows: laser power at 1750 W, scanning speed at 8.0 mm/s, and powder feed rate at 11.5 g/min. The model demonstrated strong agreement with the experimental results. The coating molding quality is exceptional, with an average porosity of 0.07 % and an average microhardness of 208.32 HV0.2. Meanwhile, the coating was composed of HCP phase and FCC phase, with the HCP phase comprising15.6 % and the FCC phase 84.4 %, respectively. Under the optimal processing parameters, the Fe50Mn30Co10Cr10 high-entropy alloy coating demonstrated impressive ductility and strength, with a deformation of 55.93 % and a compressive strength of 2153.7 MPa. The fracture mechanism of Fe50Mn30Co10Cr10 coatings is transcrystalline fracture and toughness fractures.

Track trajectory, molten pool and defect characterization in NiTi single-track selective laser melting (SLM) experiments

In order to explore the law of selective laser melting (SLM) forming of Nitinol alloy, and obtain high quality additive manufacturing parameters of Nitinol alloy, a series of single-track SLM experiments on Nitinol alloy were conducted under different combined parameters of laser power and scanning speed. The effects of laser power, scanning speed and linear energy density on track forming, molten pool evolution and pore formation were systematically discussed by characterizing the track trajectory, molten pool morphology, dimensions and defects of the molten pool, and the ideal process parameters were obtained. The experimental results revealed that the average track width and width uniformity decreased with the increase of the scanning speed, the spheroidization phenomenon and height fluctuation became more pronounced, and the phenomena of necking, subsection and interruption increased significantly at the fixed laser power. Under the fixed scanning speed, the width, height and width uniformity of the molten track gradually increased with the increase of the laser power, and the phenomena of spheroidization, subsection and interruption gradually reduced. Moreover, the upper zone of the molten pool is shaped like an inverted bowl, and the lower zone is mainly divided into five categories, which are lack of fusion, shallow bowl shape, deep bowl shape, keyhole shape and deeper keyhole shape under different process parameters. The defects of the molten pool mainly include lack of fusion and trapped gas. An ideal molten pool without defects can be obtained under the parameter conditions of 100-150W laser power and 100-200mm/s spanning speed.

Optimizing laser parameters and exploring building direction dependence of corrosion behavior in NiTi alloys fabricated by laser powder bed fusion

The microstructure and materials performance of Laser Powder Bed Fusion-fabricated (LPBFed) NiTi shape memory alloys (SMAs) varies depending on the laser parameters and building directions. This study initially optimized the laser processing parameters (laser power and scanning speed) for LPBFed NiTi SMAs to enhance their printing quality and mechanical properties. We determined that with fixed hatch spacing of 80 μm and layer thickness of 30 μm, the laser power of 105 W, and scanning speed of 600 mm/s produced the best results. Subsequently, the corrosion behavior of LPBFed NiTi SMAs built in three different building directions (0°, 45°, 90°) was investigated in 0.9 wt.% NaCl solution at 37 °C. The electrochemical data revealed that the corrosion current density (Icorr) decreased with increasing building direction angle (Icorr-90° <Icorr-45° <Icorr-0°). The corrosion resistance followed the order of 0° sample ˂ 45° sample ˂ 90° sample. These findings were attributed to the difference in the grain size and boundary density. Higher boundary densities enhanced the electron activity capacity and the element diffusion rates, facilitating the rapid formation of a protective film and thus improving the corrosion resistance. This new insight into the anisotropy of corrosion behavior relative to building directions can inform the design of NiTi-SMA products and improve their reliability in tissue engineering applications.

Microstructure and Mechanical Properties of Laser Powder Bed Fusion 3D-Printed Cu-10Sn Alloy

This study investigated the optimal process conditions and mechanical properties of Cu-10Sn alloys produced by the powder bed fusion (PBF) method. The optimal PBF conditions were explored by producing samples with various laser scanning speeds and laser power. It was found that under optimized conditions, samples with a density close to the theoretical density could be fabricated using PBF without any serious defects. The microstructure and mechanical properties of samples produced under optimized conditions were investigated and compared with a commercial alloy produced by the conventional method. The hardness, maximum tensile strength, and elongation of the samples were significantly higher than those of the commercially available cast alloy with the same chemical composition. Based on these results, it is expected to be possible to use the PBF technique to manufacture Cu-10Sn products with complex 3D shapes that could not be made using the conventional manufacturing method.

Laser surface alloying of Hastelloy X superalloy with Amdry 365 powder: Microstructural evolution and microhardness

Laser surface alloying is a surface modification technique that melts coat powder and substrate with high laser power density. This study aims to improve the properties of Hastelloy X, a Ni-based superalloy used for gas turbine components, by applying a NiCoCrAlY coating using laser surface alloying. The purpose of this study was to investigate the process parameters including laser scanning speed, laser power, and stand-off distance on the microstructure and microhardness of the alloying zones. The findings indicate that different microstructures were formed in different alloying zones such as cellular, columnar, and equiaxed. The results also revealed the presence of β and γ phases in the dendritic and interdendritic regions. The microhardness at the interface was higher than that of the other alloying areas due to the increased content of the Mo element. This study concluded that the properties of Hastelloy X can be improved by using NiCoCrAlY powder through a laser alloying process.

Influence of Process Parameters on Flatness During Single-Track Laser Cladding.

During the laser cladding process, poor flatness of the cladding track can cause the surface structure to be uneven or corrugated, affecting the geometrical accuracy of the workpiece. Adjusting process parameters is an effective way to achieve high cladding track flatness. This study established a mesoscale model of the laser cladding process for CoCrMoSi powder to simulate the formation of a single cladding track. Subsequently, the formation mechanism of cladding track flatness was revealed by analyzing the flow within the molten pool and the solidification behavior of the molten pool edge. The influences of laser power, scanning speed, and powder feeding rate on flatness were determined through simulations and physical experiments. Finally, a parameter window of flatness was established using simulation and experimental results. The window indicates that high flatness is achieved with a high scanning speed (v > 260 mm/min), high laser power (P > 2300 W), and low powder feed rate (Pf < 5.5 g/min). The accuracy of the numerical model was verified by comparing the simulated results with the experimental measurements.

Optimal process parameter determination in selective laser melting via machine learning-guided sequential quadratic programing

Selective Laser Melting (SLM) is a widely used additive manufacturing method with critical processing parameters such as Laser Power, Scanning Speed, Hatch Distance, and Laser Beam Diameter, which significantly impact process quality and mechanical properties of fabricated parts like Relative Density, Hardness, and Surface Roughness. This study investigates an effective approach to modeling the SLM process for predicting and optimizing processing parameters using a combination of Machine Learning (ML) and Sequential Quadratic Programing (SQP). The proposed method aims to predict the mechanical properties of SLM-produced AlSi10Mg parts using Machine Learning techniques and then transform the process into a constrained multiple-objective optimization model employing the SQP algorithm to determine optimal process parameters. Artificial Neural Networks (ANN), Gaussian Process Regression (GPR), and Support Vector Machine (SVM) algorithms are applied to establish correlations between process parameters and mechanical properties, represented as mathematical functions. A cost function is formulated using these functions and minimized using the SQP method. Statistical analysis is implemented to validate the influence of processing parameters on mechanical properties accordingly. The outcomes of the method are verified through additional experiments and analyses using Micro-CT scanning techniques. The results demonstrate that processing parameters have a significant impact on part properties across different scales, with Micro-CT scanning proving instrumental in validating mechanical properties. Overall, this study establishes that multiple objectives can be efficiently optimized through the integration of ML and SQP methods, complemented by a judicious number of experiments.

Research on the Mechanism of Femtosecond Laser Ablation Concave-Convex Microstructure Transformation.

The phenomenon of femtosecond laser ablation of convex structures from the bottom to the top is interesting. In this study, AZ31B magnesium alloy was used as the substrate to analyze the impact of the laser pulse energy and scanning speed on the morphology of concave-convex microstructures. Subsequently, a unified two-dimensional numerical model incorporating solid, liquid, and gas phases was established, and combined with experimental data, the mechanism and formation process of concave-convex transformation in magnesium alloy under laser ablation were revealed. The results indicate that the transition from concave to convex structures is significantly influenced by the laser scanning speed, whereas the laser pulse energy primarily affects the shape and size of the convex structures. During the ablation process, molten material is expelled and gradually accumulates on both sides of the ablation groove under the action of the recoil pressure. During cooling, the molten material at both ends of the groove merges to form protrusions under the combined effects of internal negative pressure, gravity, and Marangoni forces. Moreover, this method of femtosecond laser ablation for generating convex structures deviates from the traditional single-texture approach to concave structures, potentially broadening the application of laser composite processing surfaces.

First step toward designing effective real-time control systems in laser directed energy deposition

In-process monitoring and control are essential for quality assurance and consistency of laser-based directed energy deposition processes. Detection of irregularities during deposition in terms of defects or flaws is based on in situ monitoring of output process parameters such as temperature, melt-pool geometry, or deposition height. The real-time feedback of these output parameters allows the development of control strategies for real-time adjustment of input process parameters, such as laser power or scanning speed, to correct detected deviations from the desired output process parameters. Therefore, criteria such as sensitivity, stability, correlation, trends, and interactions of the input-output process parameters have a direct impact on controller design, establishing, for example, control limits or tolerance ranges of the output parameters. This paper focuses on the study of the characteristics of output process parameters to input process parameters. This research involves analyzing and comparing the deposition of single tracks under various input process parameters, including laser power and scanning speed. Melt-pool geometry and temperature are estimated from a visual camera and a hyperspectral line camera, whereas the final deposition geometry is obtained from a laser triangulation scanner. The results show the linearity between input and output process parameters, the steadiness of the output process parameters, the relation between melt-pool and final deposition, and offer insights to design effective in-process control systems.

Direct formation of pure copper layer on aluminum nitride by multibeam laser deposition with blue diode lasers

A demand of power module devices has been increasing for highly energy efficient social system. The insulated heat sink printed circuit board is the key component of power module devices, which is composed of copper and aluminum nitride (AlN) due to high thermal conductivity. The conventional method of the joining between copper and AlN is active metal brazing method, but there is an issue that the high heat treatment of this method generates thermal residual stress on the board and decrease the reliability. For that reason, the development of a direct bonding process between copper and AlN has been demanded. Therefore, we focused on the laser metal deposition (LMD) method, which is a selective heating and microfabrication process. The LMD method is a method in which a powder material is supplied to the processing point and irradiated with a laser to melt the powder and form layer on the surface of the substrate. Then, a blue diode laser with a wavelength of 450 nm, which has a high absorptivity of 60% for copper, is used as a heat source. In addition, the multibeam type LMD system has been installed for the uniform heating of powder. In this study, the laser power density, laser scanning speed, and powder feeding rate were changed to explore the conditions for forming a copper layer on the AlN substrate.