Search Results (398)

Ultrasonic-assisted laser-directed energy deposition (UA-DED) is a promising combined technology for manufacturing high-value thin-walled Inconel 718 components in aerospace. Nevertheless, the optimal ultrasonic frequency—a key parameter for achieving desirable performance in thin-walled Inconel 718 alloys—remains to be determined. In this study, we systematically investigated the influence of ultrasonic frequency (12–20 kHz) on the microstructure and mechanical properties of thin-walled Inconel 718 fabricated by UA-DED. The results revealed that an ultrasonic frequency of 20 kHz was optimal and can yield significant improvements in the microstructures of the as-deposited sample coordinate planes, manifested by the complete suppression of large pores, three-dimensional refinement of the γ matrix grains, alleviation of Nb and Mo segregation, the reduction of fragmented Laves particles, a decrease in residual macroscopic stresses, and homogeneous distributions of γ′/γ″ phases and γ-grain orientation. Meanwhile, the application of a 20 kHz ultrasonic frequency endows the manufactured thin-walled 718 parts with superior mechanical properties, including a tensile strength of 899 MPa in the laser scanning direction and 877 MPa in the build direction, along with the corresponding elongations of 34.8% and 38.9%. This work demonstrates the potential of modulating ultrasonic frequency to tailor microstructures and produce high-performance thin-walled Inconel 718 aerospace components. Full article

The present work uses numerical methods to explore the impact of spatial orientation on the behavior of molten pool and thermal responses during the laser–Cold Metal Transfer (CMT) hybrid additive manufacturing of metallic cladding layers. Based on the traditional double-ellipsoidal heat source model, an adaptive CMT arc heat source model was developed and optimized using experimentally calibrated parameters to accurately represent the coupled energy distribution of the laser and CMT arc. The improved model was employed to simulate temperature and velocity fields under horizontal, transverse, vertical-up, and vertical-down orientations. The results revealed that variations in gravity direction had a limited effect on the overall molten pool morphology due to the dominant role of vapor recoil pressure, while significantly influencing the local convection patterns and temperature gradients. The simulations further demonstrated the formation of keyholes, dual-vortex flow structures, and Marangoni-driven circulation within the molten pool, as well as the redistribution of molten metal under different orientations. In multi-layer deposition simulations, optimized heat input effectively mitigated excessive thermal stresses, ensured uniform interlayer bonding, and maintained high forming accuracy. This work establishes a comprehensive numerical framework for analyzing orientation-dependent heat and mass transfer mechanisms and provides a solid foundation for the adaptive control and optimization of laser–CMT hybrid additive manufacturing processes. Full article

Directed Energy Deposition-Laser (DED-L) enables high-performance coatings through melting and successive powder deposition. Its compositional flexibility suits functionally graded layers that enhance corrosion and wear resistance. This study aimed to improve parameters for producing dense, defect-free, graded Ni- and Fe-based coatings by varying the scanning speed and deposition strategy (monodirectional versus bidirectional, with/without layer rotation), while keeping the power and hatch distance constant. Laser and electron microscopy were used to link parameters to porosity and uniformity. Optimal settings minimized pores, improved interlayer bonding and preserved geometry; inadequate parameters yielded porous, irregular deposits. A bidirectional path with 90° rotation appeared best. Ongoing research activities are needed to assess its properties. Full article

Directed Energy Deposition (DED), as a core branch of additive manufacturing, encompasses two typical processes: laser directed energy deposition (LDED) and wire and arc additive manufacturing (WAAM), which are widely used in manufacturing aerospace engine blades and core components of high-end equipment. In recent years, with the increasing adoption of deep learning (DL) technologies, the research focus in DED has gradually shifted from traditional “process parameter optimization” to “AI-driven process optimization” and “online real-time monitoring”. Given the complex and distinct influence mechanisms of key parameters (such as laser power/arc current, scanning/travel speed) on melt pool behavior and forming quality in the two processes, the introduction of artificial intelligence to address both common and specific issues has become particularly necessary. This review systematically summarizes the application of DL techniques in both types of DED processes. It begins by outlining DL frameworks, such as artificial neural networks (ANNs), recurrent neural networks (RNNs), convolutional neural networks (CNNs), and reinforcement learning (RL), and their compatibility with DED data. Subsequently, it compares the application scenarios, monitoring accuracy, and applicability of AI in DED process monitoring across multiple dimensions, including process parameters, optical, thermal fields, acoustic signals, and multi-sensor fusion. The review further explores the potential and value of DL in closed-loop parameter adjustment and reinforcement learning control. Finally, it addresses current bottlenecks such as data quality and model interpretability, and outlines future research directions, aiming to provide theoretical and engineering references for the intelligent upgrade and quality improvement of both DED processes. Full article

Multi-material Directed Energy Deposition (DED) Additive Manufacturing (AM) processes enable the integration of different material properties into a single structure, addressing the requirements of various applications and working environments. Laser-based Directed Energy Deposition (DED-LB) has been employed in the past for surface coatings as well as for the repair and repurposing of high-value industrial components, with the goal of extending product lifetime without relying on expensive and time-consuming manufacturing from scratch. While powder DED-LB has traditionally been used for multi-material AM, the more resource-efficient and cost-effective wire DED-LB process is now being explored as a solution for creating hybrid materials. This work focuses on the critical aspects of implementing multi-material DED-LB, specifically defining an optimal operating process window that ensures the best quality and performance of the final parts. By investigating the possibility of combining stainless steel and nickel-based alloys, this study seeks to unlock new possibilities for the repair and optimization of naval components, ultimately improving operational efficiency and reducing downtime for critical naval equipment. The analysis of the experimental results has revealed strong compatibility of stainless steel 316 with Inconel 718 and stainless steel 17-4PH, while the gray cast iron forms acceptable fusion only with stainless steel 17-4PH. Finally, during the experimental phase, substrate pre-heating and process monitoring with thermocouples will be employed to manage and assess heat distribution in the working area, ensuring defect-free material joining. Full article

This study investigates the effect of Interlayer Dwell Time (IDT) on the thermal behavior of the Wire-Laser Directed Energy Deposition (WLDED) process. A two-dimensional transient thermal model was developed in MATLAB, incorporating temperature-dependent material properties, a moving Gaussian heat source, and melting–solidification phase change to simulate sequential layer deposition. The model was calibrated for thin-walled geometries, numerically validated using ANSYS, and experimentally validated with literature data. Using the validated model, twenty-seven cases were simulated to examine the combined influence of IDT, part length, and layer thickness on melt-pool dimensions and layer-wise temperature distribution. The results show that increasing IDT reduces melt-pool depth and length by limiting heat accumulation, with the magnitude of this effect depending strongly on part length and layer thickness. Shorter parts and thicker layers exhibit the highest sensitivity to IDT variations. Additionally, the Thermal Stability Factor (TSF) is introduced, a dimensionless index that effectively identifies heat-accumulation phenomena and indicates thermal instabilities. Overall, the findings enhance the understanding of the impact of IDT in the thermal profile of WLDED and demonstrate that optimized IDT selection can stabilize melt-pool geometry and reduce thermal buildup, supporting future adaptive IDT strategies in wire-based metal additive manufacturing. Full article

Cobalt-based superalloy Co06A exhibits excellent high-temperature performance and is widely used in the repair and additive manufacturing of critical hot-end components via direct laser deposition (DLD). However, improper energy–mass input during direct laser deposition often leads to defects such as porosity, cracks, and poor surface quality, which seriously affect the performance of formed parts. In this study, a systematic experimental investigation based on an orthogonal design was carried out to examine the effects of laser power, scan speed, and powder feed rate on the dilution rate, surface roughness, and powder capture efficiency of a one-layer single Co06A track. Range analysis and multiple linear regression were employed to quantify the influence of each parameter. The results showed that the powder feed rate was the dominant factor affecting both η and Sa, while the laser power had the most significant impact on PE. Through multi-objective optimization, a balanced parameter set (u = 6.66 mm/s, f = 20.81 g/min, P = 2543 W) was recommended, which achieved a dilution rate of about 11.95%, a surface roughness of 4.64 um, and a powder capture efficiency of 79.6%. Through testing, it was found that the energy/mass input ratio was approximately 8. This work demonstrated that matching energy–mass input and adopting a constrained optimization strategy could effectively improve the forming quality and manufacturing efficiency of Co06A in the first-layer manufacturing process, providing a promising prospect in guidance for engineering applications. Full article

The rapid advancement of high-performance electronics has intensified the demand for wide-bandgap semiconductor materials capable of operating under high-power and high-temperature conditions. Among these, silicon carbide (SiC) has emerged as a leading candidate due to its superior thermal conductivity, chemical stability, and mechanical strength. However, the high cost and complexity of SiC wafer fabrication, particularly in slicing and exfoliation, remain significant barriers to its widespread adoption. Conventional methods such as wire sawing suffer from considerable kerf loss, surface damage, and residual stress, reducing material yield and compromising wafer quality. Additionally, techniques like smart-cut ion implantation, though capable of enabling thin-layer transfer, are limited by long thermal annealing durations and implantation-induced defects. To overcome these limitations, ultrafast laser-based processing methods, including laser slicing and stealth dicing (SD), have gained prominence as non-contact, high-precision alternatives for SiC wafer exfoliation. This review presents the current state of the art and recent advances in laser-based precision SiC wafer exfoliation processes. Laser slicing involves focusing femtosecond or picosecond pulses at a controlled depth parallel to the beam path, creating internal damage layers that facilitate kerf-free wafer separation. In contrast, stealth dicing employs laser-induced damage tracks perpendicular to the laser propagation direction for chip separation. These techniques significantly reduce material waste and enable precise control over wafer thickness. The review also reports that recent studies have further elucidated the mechanisms of laser–SiC interaction, revealing that femtosecond pulses offer high machining accuracy due to localized energy deposition, while picosecond lasers provide greater processing efficiency through multipoint refocusing but at the cost of increased amorphous defect formation. The review identifies multiphoton ionization, internal phase explosion, and thermal diffusion key phenomena that play critical roles in microcrack formation and structural modification during precision SiC wafer laser processing. Typical ultrafast-laser operating ranges include pulse durations from 120–450 fs (and up to 10 ps), pulse energies spanning 5–50 µJ, focal depths of 100–350 µm below the surface, scan speeds ranging from 0.05–10 mm/s, and track pitches commonly between 5–20 µm. In addition, the review provides quantitative anchors including representative wafer thicknesses (250–350 µm), typical laser-induced crack or modified-layer depths (10–40 µm and extending up to 400–488 µm for deep subsurface focusing), and slicing efficiencies derived from multi-layer scanning. The review concludes that these advancements, combined with ongoing progress in ultrafast laser technology, represent research opportunities and challenges in transformative shifts in SiC wafer fabrication, offering pathways to high-throughput, low-damage, and cost-effective production. This review highlights the comparative advantages of laser-based methods, identifies the research gaps, and outlines the challenges and opportunities for future research in laser processing for semiconductor applications. Full article

By employing graded-interfaces modeling, ~10 μm-emitting quantum cascade lasers (QCLs) are designed with previously found conditions for record-high wall-plug efficiency (WPE) operation of mid-infrared QCLs: direct resonant-tunneling injection from a prior-stage low-energy state into the upper-laser level, photon-induced carrier transport, and carrier-leakage suppression via the step-taper active-region (STA) approach. For devices with interface-roughness (IFR) parameters characteristic of optimized molecular-beam-epitaxy (MBE) growth, a maximum front-facet pulsed WPE value of 19.6% is projected for 60-stages STA-type devices. This results from several factors: 19 mV voltage defect at threshold, 72% voltage efficiency at the maximum WPE point, and ~93% injection efficiency due to strong carrier-leakage suppression. 2.7 W peak front-facet power is projected. For devices with our metal–organic chemical vapor deposition (MOCVD)-growth IFR parameters, the projected maximum pulsed WPE value is 17.1%, i.e., 1.7 times higher than the highest reported front-facet WPE value from ~10 μm-emitting MOCVD-grown QCLs. Studies regarding the WPE value variation with the stage number, while employing waveguide designs having the same empty cavity loss, reveal that the maximum WPE value remains almost the same for 50–60 stages devices. In turn, there is potential for obtaining significantly higher CW powers than from conventional ~10 μm-emitting QCLs. Full article

The wire Laser-based Directed Energy Deposition (DED-LB) metal additive manufacturing (AM) process is time- and cost-effective, providing high-quality, dense parts while supporting multi-scale manufacturing, repair, and repurposing services. However, its ability to consistently produce parts of uniform quality depends on process stability, which can be achieved through monitoring and controlling key process phenomena, such as heat accumulation and variations in the distance between the deposition head and the working surface (standoff distance). Part quality is closely linked to achieving predictable melt pool dimensions and stable thermal conditions, which in turn influence the end-part’s cross-sectional stability, overall dimensions, and mechanical properties. This work presents a workflow that correlates process and metrology data, enabling the determination of tunable process parameters and their operating process window. The process data are acquired using a vision-based monitoring system and a load-cell embedded in the deposition head, which together detect variations in melt pool area and standoff distance during the process, while metrology devices assess the part quality. Finally, this monitoring setup and its ability to capture the complete process history are fundamental for developing in-line control strategies, enabling optimized, supervision-free, and repeatable processes. Full article

Heterostructure (HS) refers to a class of structural materials composed of two or more different chemical components or crystal structures. Integration of Inconel 625 (IN625) nickel-based superalloy and Ti6Al4V (TC4) titanium alloy to a HS material offers a promising strategy to achieve graded thermo-mechanical properties, extended service temperature ranges, and significant weight reduction, which are highly desirable in aerospace applications. However, obtaining a better metallurgical bonding between the two alloys remains a critical challenge. In this study, laser directed energy deposition (L-DED) technology was employed to fabricate IN625/TC4 HS materials with a nonlinear gradient transition, following systematic investigations into the phase composition and crack sensitivity of IN625/TC4 gradient layers prepared from mixed powders of varying compositions. In addition, microstructure, phase distribution, and mechanical properties of HS materials at room temperature were characterized. The metallurgical defect-free IN625/TC4 HS material was successfully prepared, featuring a smooth transition of microstructure, reduced cracking sensitivity, and reliable metallurgical bonding. Furthermore, a novel design concept and illustrative reference for the L-DED fabrication of N625/TC4 HS material with excellent comprehensive performance was presented, while providing a theoretical metallurgical basis and data support for the potential applications of IN625/TC4 HS materials in the field of aerospace. Full article

In this study, TiB₂/AlSi10Mg, 2 wt.% SiC + TiB₂/AlSi10Mg, and 5 wt.% SiC + TiB₂/AlSi10Mg composite powders were prepared via high-energy ball milling. For the first time, TiB₂ and SiC hybrid particle-reinforced aluminum matrix composites (AMCs) were fabricated using the Laser-Directed Energy Deposition (LDED) technique. The effects of processing parameters on the microstructure evolution and mechanical properties were systematically investigated. Using areal energy density as the main variable, the experiments combined microstructural characterization and mechanical testing to elucidate the underlying strengthening and failure mechanisms. The results indicate that both 2 wt.% and 5 wt.% SiC + TiB₂/AlSi10Mg composites exhibit excellent formability, achieving a relative density of 98.9%. However, the addition of 5 wt.% SiC leads to the formation of brittle Al₄C₃ and TiC phases within the matrix. Compared with the LDED-fabricated AlSi10Mg alloy, the tensile strength of the TiB₂/AlSi10Mg composite increased by 21.4%. In contrast, the tensile strengths of the 2 wt.% and 5 wt.% SiC + TiB₂/AlSi10Mg composites decreased by 3.7% and 2.6%, respectively, mainly due to SiC particle agglomeration and the consumption of TiB₂ particles caused by TiC formation. Nevertheless, their elastic moduli were enhanced by 9% and 16.3%, respectively. Fracture analysis revealed that the composites predominantly exhibited ductile fracture characteristics. However, pores larger than 10 μm and SiC/TiB₂ clusters acted as crack initiation sites, inducing stress concentration and promoting the propagation of secondary cracks. Full article

Although Directed Energy Deposition (DED) of Ti–6Al–4V has been widely explored for its mechanical performance, the combined influence of build orientation and surface position (upskin/downskin) on passive film kinetics and fluoride-induced degradation remains largely unexamined. This study addresses this gap by systematically investigating how processing direction and surface thermal history govern microstructure and corrosion behaviour in Laser-Based DED (LB-DED) Ti–6Al–4V. The alloy was fabricated in XY and XZ orientations, and both upskin and downskin surfaces were evaluated. Microstructural characterisation revealed strong anisotropy, with elongated prior-β grains and directional α + β colonies particularly prominent in the XZ orientation. Electrochemical testing in borate buffer showed stable passivity across all conditions, with XY surfaces forming the most compact oxide films. In a more aggressive 2.5% NaF saliva environment, substantial orientation-dependent degradation was observed: XY specimens maintained low corrosion currents and uniform passive layers, whereas XZ downskin exhibited unstable passivation and extensive micro-pitting. These findings demonstrate, for the first time, that the interplay between build orientation and surface position critically dictates passive film defect structure, stability, and fluoride-driven breakdown, providing new mechanistic insight into the corrosion behaviour of DED Ti–6Al–4V relevant to biomedical applications. Full article

This study presents the development and validation of an in situ monitoring method for the laser direct energy deposition (DED) process, utilizing an integrated optical camera (720 HD, 60 fps) to analyze melt pool imagery. The approach is grounded in an experimental framework employing Taguchi orthogonal arrays, which ensures a stable dataset by controlling process variability and enabling reliable extraction of relevant features. The monitoring system focuses on analyzing brightness distribution regions within the melt pool image, identified as specific clusters that reflect external process conditions. The method emphasizes precise segmentation of the melt pool area, combined with automatic detection and classification of cluster features associated with key process parameters—such as focus distance, the number of deposited layers, powder feed rate, and scanning speed. The main contribution of this work is demonstrating the effectiveness of using an optical camera for DED monitoring, based on an algorithm that processes a set of melt pool identification features through computer vision and machine learning techniques, including Random Forest and HistGradient Boosting, achieving classification accuracies exceeding 95%. By continuously tracking the evolution of these features within a closed-loop control system, the process can be maintained in a stable, defect-free state, effectively preventing the formation of common process defects. Full article

Laser wire additive manufacturing (LWAM) offers high deposition efficiency and excellent material utilization. However, manufacturing thin-walled structures with large inclination angles and no support remains a challenge. In this study, the influence of laser tilt angle on the formability of multi-layer inclined parts was systematically investigated. Results reveal that tilting the laser redistributes energy input along the inclination direction, stabilizing the melt pool and reducing angular deviation. Under a 20° tilt condition, thin-walled structures with inclination up to 70° were successfully fabricated, overcoming the limitation of conventional vertical deposition. Furthermore, a multi-inclination arch bridge structure was fabricated under optimized conditions, demonstrating good morphological appearance, dimensional accuracy (deviation within ±0.3 mm), and surface waviness (W < 0.12 mm). The findings provide new insights into the mechanism of energy redistribution in tilted LWAM and establish a promising strategy for manufacturing complex overhanging structures in aerospace and automotive industries. Full article