Direct Deposition Research Articles

Development of a gas metal arc based prototype for direct energy deposition with micrometric wire

In recent years, efforts have been focused on the development of metal additive manufacturing (AM) processes to address the growing trend of miniaturization in industries such as aerospace and electronics. Thus, new technologies have been developed based on a downscaled approach using direct energy deposition (DED) processes, now referred to as μ-DED. In this context, the development of a downscaled DED prototype based on gas metal arc (GMA) working with micrometric wires (μ-GMA) has the potential to unify the positive characteristics of GMA-based DED, increasing the complexity of the design and resolution of the produced parts. Therefore, this work focuses on developing a μ-GMA prototype and assessing its technical feasibility. This paper describes the development of the μ-GMA prototype, characterizes the metallic transfer mode, and statistically analyzes the effect of deposition parameters on bead width and height. Additionally, microstructural analysis, Vickers microhardness, and reduced Young's modulus tests were performed. The μ-GMA prototype demonstrated the capability to deposit beads with an approximate width of 1 mm, nearly 5 times thinner than standard GMA-based DED deposition, with a build rate of 30 cm3/h, which is lower than GMA-based DED but higher than other μ-DED processes. Furthermore, the mechanical properties of the μ-GMA depositions are comparable to regular GMA-based DED parts.

Oxidation Behavior of Ni-Based Oxide Dispersion-Strengthened Alloy Fabricated by Direct Energy Deposition at 1100 °C

Oxidation Behavior of Ni-Based Oxide Dispersion-Strengthened Alloy Fabricated by Direct Energy Deposition at 1100 °C

Investigations on mass flow rate of rotary vane feeder for direct metal laser deposition

Investigations on mass flow rate of rotary vane feeder for direct metal laser deposition

Accelerated semantic segmentation of additively manufactured metal matrix composites: Generating datasets, evaluating convolutional and transformer models, and developing the MicroSegQ+ Tool

Data-driven applications are penetrating every aspect of Additive Manufacturing (AM) to enable efficient resolution of key existing challenges. One such application is semantic segmentation which automatically quantifies post-process structure data from graphic or 3D computer representations. In industrial settings, these models can expedite the development of new materials or processes. However, Additively Manufactured (AMed) materials offer unique challenges, which require new models to be developed and trained. These challenges include out-of-balance classes (e.g., defects), massive labeling efforts, and significant data preparation costs. Recent applications of semantic segmentation in AM have shown the potential of ensemble-based approaches at the expense of increased parameters and computational burden while ignoring the minority classes. In this work, we propose a reproducible method and develop an associated tool to rapidly segment and subsequently quantify industrial AMed metallographic images. First, two new datasets representing AMed materials are generated from extensive experimentation. Subsequently, state-of-the-art models from convolutional and self-attention categories are evaluated in their ability to segment the datasets of interest. Finally, a modular software tool is developed for industrial applications. The developed Microstructure Segmentation, Quantification, and Fusion (+) tool or MicroSegQ+ enables a weighted pairing of predictions from different semantic segmentation models. The pairing strategy helps to exploit the complimentary performance of convolutional and transformer models on multi-class metallographic images from a Metal Matrix Composite (MMC) material system. In addition to developing models on this MMC dataset, the proposed strategy is evaluated on an open-source metal AM dataset. We also evaluate the generalizability of the best-performing model on a second MMC dataset from a different industrial setting that shows an overall accuracy of 93 % without fine-tuning. The proposed tool enables rapid quantification under 1 min, unlike the existing semi-automatic approach that takes 1–2 h of segmentation effort on single bead cross-sections. The tool is wrapped into a single executable file for industrial deployment. The work also contributes to two annotated datasets from a direct energy deposition (DED) AM process. The datasets can be used to develop and validate new semantic segmentation models of AMed microstructures, whereas the functionality of the tool can be expanded upstream to include data and modeling steps, enabling a no-code pipeline for the industry.

Optimization of single-track deposits in wire arc-based direct energy deposition of ER110S-G steel using MONS-MFO and TOPSIS algorithms

Wire and arc-based direct energy deposition (wire and arc DED) is a promising metallic additively manufacturing (MAM) technology to fabricate large-size metallic components. Among high-strength-low-alloy steels used in wire and arc DED processes, ER110S-G is a commonly used material. However, previous studies have often relied on process parameters recommended by suppliers for conventional welding methods. This study aims to predict the optimum processing parameters for the manufacture of ER110S-G steel by a wire and arc DED process based on experiment and multi-attribute optimization algorithms. The experiment was designed using the full factorial method with the input variables ( U– voltage, I– current, and v– traveling speed) while considering three attributes of single tracks ( STW– single track width, STH– single track height, and LMP– length of melting pool). To find the optimal processing variables, MONS-MFO (Multi-Objective Non-Sorted Moth Flame) was utilized. The outcomes reveal that the developed predictive models of attributes feature a high accurate level ( R2 = 98.11%, 98.38%, and 98.07% for STW, STH, and LMP, respectively). The optimal parameters obtained by MONS-MFO & TOPSIS were I = 159.4 A, v = 0.3 m/min, and U = 21.4 V allow fabricating single tracks with smooth and regular shape and a s-shaped thin-wall component with regular shape and height. Moreover, no spatters generated with the optimal parameters, demonstrating their suitability and efficiency for the printing process.

In Situ Bioprinting: Process, Bioinks, and Applications.

Traditional tissue engineering methods face challenges, such as fabrication, implantation of irregularly shaped scaffolds, and limited accessibility for immediate healthcare providers. In situ bioprinting, an alternate strategy, involves direct deposition of biomaterials, cells, and bioactive factors at the site, facilitating on-site fabrication of intricate tissue, which can offer a patient-specific personalized approach and align with the principles of precision medicine. It can be applied using a handled device and robotic arms to various tissues, including skin, bone, cartilage, muscle, and composite tissues. Bioinks, the critical components of bioprinting that support cell viability and tissue development, play a crucial role in the success of in situ bioprinting. This review discusses in situ bioprinting techniques, the materials used for bioinks, and their critical properties for successful applications. Finally, we discuss the challenges and future trends in accelerating in situ printing to translate this technology in a clinical settings for personalized regenerative medicine.

Achieving strong and ductile Ti-9Cr alloy with deformable TiCr2 nano-particles by direct energy deposition

Due to the strong segregation of Cr, the content of Cr was restricted in the commercial titanium alloy to avoid β-flecks and deterioration of mechanical performance. Here, we prepared a homogeneous Ti-9Cr alloy with uniform distribution of Cr element by additive manufacturing technology. Fine α laths and dispersed TiCr2 nano-particles were acquired in the alloy, generating a high ultimate tensile strength of 1000 MPa with elongation of 16 %. It was demonstrated that the TiCr2 nano-particles showed a face-centered cubic structure. Stacking faults occurred on the {111} plane of the TiCr2 during deformation, which relieved local stress.

Rare-earth doped yttrium silicate (Y2SiO5) thin films grown by chemical vapour deposition for quantum technologies

Yttrium orthosilicate (Y2SiO5 - YSO) is one of the most promising crystals to host rare-earth (RE) ions for quantum technologies applications. In this matrix, they indeed exhibit narrow optical and spin linewidths that can be exploited to develop quantum memories or quantum information processing capabilities. In this paper, we propose a new method to grow RE doped silicate thin films on silicon wafers based on direct liquid injection chemical vapour deposition (DLI-CVD). We optimize the deposition and annealing conditions to achieve formation of the high temperature X2-YSO phase. The phase purity and crystalline quality of the films are assessed by evaluating the optical properties of Eu3+ ions embedded in this oxide matrix. In view of the results, we discuss the possible phase formation mechanisms, and the potential of this new wafer-compatible form of YSO for quantum technologies applications.

Wear Behavior Assessment of New Wire-Arc Additively Manufactured Surfaces on AA6061 and AA5086 Alloys through Multi-Walled Carbon Nanotubes and Ni Particles Inducement

This study investigates the new surface development on AA6061 and AA5086 alloys considering the wire-arc additive manufacturing technique as a direct energy deposition (DED) process of wire. Two different quantities of MWCNTs, i.e., 0.01 (low) and 0.02 (high) g, with a constant nickel (Ni) weight (0.2 g) were pre-placed in the created square patterns. ER4043 filler was used as a wire for additive deposition, and an arc was generated through a tungsten inert gas (TIG) welding source. Furthermore, hardness and pin-on-disk wear-testing methods were employed to measure the changes at the surfaces with the abovementioned inducements. This work was designed to illustrate the hardness and the offered wear resistance in terms of mass loss of the AA6061 and AA5086 aluminum alloys with the function of nano-inducements. Two sliding distance values of 500 m and 600 m were selected for the wear analysis of mass loss from tracks. A maximum increase in hardness for AA6061 and AA5086 alloys was observed in the experiments, with average values of 70.76 HRB and 74.86 HRB, respectively, at a high mass content of MWCNTs. Moreover, the tribological performance of the modified surfaces improved with the addition of MWCNTs with Ni particles in a broader sense; the modified surfaces performed exceptionally well for AA5086 compared to AA6061 with 0.02 and 0.01 g additions, respectively. The system reported a maximum of 38.46% improvement in mass loss for the AA5086 alloy with 0.02 g of MWCNTs. Moreover, the morphological analysis of the developed wear tracks and the mechanism involved was carried out using scanning electron microscope (SEM) images.

Crack healing via electropulsing treatment applied to additive-manufactured TiC/316L stainless steel composites

Three coupons of TiC/316L stainless steel composites were fabricated by laser-based directed energy deposition (DED-LB). One coupon is crack-free, and the other two coupons have cracks inside. Electropulsing treatment (EPT) was applied to heal the cracks, with various current densities and 75 pulses on each sample. The cracks with widths of 0–200 μm can be healed by EPT. The microstructure of the healed region consists of refined fractured TiC particles and resolidified fine austenite grains. The EPT is able to potentially be applied to heal the defects or cracks in additive-manufactured metal-matrix composites.

The effect of the laser beam intensity profile in laser-based directed energy deposition: A high-fidelity thermal-fluid modeling approach

Modeling the thermal and fluid flow fields in laser-based directed energy deposition (DED-LB) is crucial for understanding process behavior and ensuring part quality. However, existing models often fail to accurately predict these fields due to simplifying assumptions, particularly regarding powder particle-induced attenuation in laser power and energy density distribution, and the variable material properties and process parameters. The present work introduces a high-fidelity multi-phase thermal-fluid model driven by a combination of the discrete element method (DEM) and the finite volume method (FVM). Incorporating an enhanced attenuation model for laser energy enables a more precise approximation of powder particle-induced attenuation effects in the laser power and energy density distribution. The study focuses on the influence of laser beam intensity profiles during DED-LB of austenitic stainless steel (AISI 316 L), with model validation conducted through experimental measurements of deposited track dimensions for different beam shapes. The results of numerical simulations demonstrate the critical impact of powder-induced attenuation on the laser power and intensity profiles. Neglecting laser energy attenuation, a common assumption in numerical simulations of DED-LB, leads to overestimations of the absorbed energy of the laser beam, affecting thermal and fluid flow fields, and melt pool dimensions. The present study unravels the complex relationship between the attenuation coefficient (due to the powder stream) and powder stream characteristics, describing the variations of the attenuation coefficient with changes in the powder mass flow rate and powder stream incidence angle. The findings show the critical effects of laser beam shaping on melt pool behavior in DED-LB, with square beams inducing larger melt pool volumes and circular beams creating smaller but deeper melt pools. The proposed enhanced thermal-fluid modeling framework offers a robust approach for optimizing laser-based additive manufacturing across diverse materials and laser systems.

Deposition mechanism of ceramic reinforced metal matrix composites via cold spraying

Understanding the mechanism underlying metal matrix composites (MMCs) in cold spraying is critical to fabricate innovative MMC coatings and deposits with tailored microstructures and excellent mechanical performance. In this work, we propose a systematic numerical simulation framework combined with experimental observations to reveal the co-deposition mechanism of cold-sprayed metal/ceramic MMCs. The finite element modeling results and experimental validation found some critical conclusions regarding the deposition mechanism. The modeling results show that most of alumina particles are significantly fractured in Inconel718/alumina coating in contrast to aluminum/alumina coating. This fact suggests that the critical fragmentation velocity (CFV) of ceramic particles is dependent on the hardness of the metal substrate/matrix. Ceramic particles are more prone to fracture when co-deposited with metals having high hardness. Moreover, the simulation results also indicate that the rebounded alumina particles or fragments are possibly captured by incoming metal particles and trapped into MMCs. Since intact alumina particles are barely seen in composites, especially when co-deposited with hard metals, it can be concluded that direct ceramic particle deposition significantly relies on fragmentation. In addition, secondary fragmentation plays a key role in the metal-ceramic co-deposition process. The particles that have completed the impact process may be subjected to secondary fragmentation in the form of new cracks and fragmentation due to the impact by following metal and ceramic particles.

Addressing the strength-corrosion tradeoff in 316 L stainless steel by introducing cellular ferrite via directed energy deposition

Typical cellular structure composed of high-density dislocation tangle can lead to high strength in directed energy deposition 316 L stainless steel, but with reduced corrosion resistance in acid solution due to accompanied element segregation. Herein, a unique cellular structure consisting of a ferrite phase is manufactured to address the strength-corrosion tradeoff via a direct energy deposition process. The relationship between strength and microstructural features, such as grain type, ferrite phases, and dislocations, as well as the relationships between corrosion resistance and these microstructural characteristics, are identified. Cellular ferrite retains the beneficial effect of the cellular structure on increasing strength and changes the material from a pure austenitic phase to an austenite-ferrite biphasic structure. The ferrite phase has a lower corrosion potential, which promotes the rapid formation of Cr- and Mo-rich corrosion product layers. It can avoid the unfavorable effects of element segregation and suppress the corrosion rate in acid solution. This study shows that directed energy deposition has the potential to customize the microstructure through a printing process that introduces a cellular ferrite phase to improve its corrosion resistance in acidic solutions as well as its strength and ductility.

Microstructure, mechanical and corrosion study of friction stir processed Inconel 625 additive layers deposited via wire arc direct energy deposition

This study explores the application of friction stir processing (FSP) as an effective post-deposition surface treatment technique for improving the mechanical and corrosion properties of wire arc direct energy deposited (WA-DED) Inconel 625 additive layers. The coarse and cube-oriented microstructure observed in as-built Inconel 625 components results in anisotropic mechanical properties. The non-equilibrium solidification in WA-DED Inconel 625 leads to severe micro-segregation of alloying elements, forming large Nb and Mo-rich Laves and carbide phases in the inter-dendritic areas. This causes a heterogeneous distribution of vital alloying elements within the γ-Ni matrix of the material, adversely affecting its mechanical properties and corrosion resistance, thereby restricting the utility of this manufacturing technique in critical applications. The incorporation of FSP has been observed to successfully eradicate the presence of typical coarse and highly oriented microstructure through grain refinement, achieving a more uniform microstructure. Through severe plastic deformation (SPD), coarse eutectic phases are broken down and redistributed within the γ-Ni matrix, enhancing the uniformity of material properties. The research thoroughly investigates the changes in microstructure, mechanical performance, and corrosion resistance of both WA-DED and FSP-enhanced WA-DED Inconel 625 samples. A Thermo-Calc simulation using the classical Scheil model was conducted to understand the solidification pathway and the formation mechanism of the Laves phase in the WA-DED sample. The grain size was significantly reduced by 98.23%, from 138 µm in the WA-DED sample to 2.44 µm in the stir zone (SZ) of the FSP-treated area, due to dynamic recrystallization (DRX), particle-stimulated nucleation (PSN), and the Zener pinning effect. This grain refinement led to remarkable enhancements in the yield strength (YS) by approximately 113%, ultimate tensile strength (UTS) by about 37% and micro-hardness by around 60% compared to the WA-DED sample. In a 3.5 wt% NaCl solution, the FSP-treated sample demonstrated superior corrosion resistance by forming a stable, thicker passive film than the as-built sample. The results of this study will offer valuable insights into utilizing the FSP technique as post-weld surface treatment of WA-DED deposited IN625 superalloy.

Evaluating the microstructural formation in Mo added Ti6Al4V alloy fabricated by direct energy deposition using a laser-stop strategy

The microstructure formation in the Ti64 alloy with the addition of different alloying elements is extensively researched to enhance the mechanical properties of the alloy, especially fabricated using additive manufacturing processes. In this work, the effect of Mo (0, 1, 2, 4 wt%) addition on the microstructure and mechanical properties of the direct energy deposited (DED) Ti64 alloy was evaluated in detail. As the Mo content increases, a remarkable refinement in the α-laths morphology was observed, with the average width decreasing from ∼1.12 μm to ∼0.39 μm, and an anomalous increase in the volume fraction of the α phase was noted in the Ti64–1Mo alloy. Further increase of the Mo content results in the attenuation of the variant dominance of the α-laths until virtually eliminated. Notice that the tensile strength and elongation increased by 7.3% and 37.5% with 1 wt% addition of Mo, respectively. A Laser-Stop (LS) strategy was employed to preserve the formed metastable phases during the DED process. Such LS strategy provides necessary insights into microstructural evolution and elucidates the mechanisms behind the formation of a refined microstructure and in turn its mechanical properties.

Microstructural evolution of a printed AISI 303 upcycled powder on a dissimilar substrate

Additive manufacturing for new constructions or repairing purposes may deal with the use of dissimilar materials. Hence, the influence of interface between the substrate layer and printed one is crucial. This study delves into the impact of printed layers on the microstructure and hardness of an upcycled AISI 303 alloy produced by Direct Energy Deposition. Chemical composition distribution, phase and grain size evolutions were studied, accompanied with microhardness measurements.Microscopic analysis through chemical composition mapping and using electron backscatter diffraction technique for crystallography analysis revealed that the interface structure is strongly affected by the distribution of chemical composition and the heat received from subsequent printing. That means, a dominant transformation of austenite to martensite/ferrite occurs at the first layer printed on the top of the substrate. This is confirmed by hardness measurements (442 ± 15 HV0.1). This dominance (global martensite/ferrite distribution of 42%) is attributed to the reduction of Cr, Ni and Mn contents in the first layer, caused by Marangoni convection currents. This study confirms that subsequent printing favors the evolution of martensite/ferrite to austenite (global distribution of 75%) and grain growth, leading to hardness decrease to around 295 ± 34 HV0.1, leaving small difference with the printed AISI 303 alloy with a hardness of 235 ± 18 HV0.1.

Microstructure and fracture toughness of a Nb–Ti–Si-based in-situ composite fabricated by laser-based directed energy deposition

Laser-based directed energy deposition (LDED), a significant integrated preparation technique combining material design and production, has been progressively used to manufacture Nb–Ti–Si-based in-situ composites. However, it is commonly known that Nb–Si-based in-situ composites have low room-temperature fracture toughness. Herein, we have designed a novel Nb–40Ti–10Si–5Al–2V (at.%) composite, the microstructure of LDED-built composite is made up of Nbss and γ-Nb5Si3, the formation of γ-Nb5Si3 precipitate in the Nbss phase with an orientation relationships (ORs) of [1110]γ//[011]Nbss, (10 1‾ 0)γ//(011)Nbss and (1 2‾ 11)γ//(200)Nbss. The composite has Nbss, Nb3Si and γ-Nb5Si3 phases after heat treatment at 1400 °C for 30 h, and δ-Nb11Si4 precipitate has formed in the Nbss phase with an ORs of [100]Nbss//[010]δ, (010)Nbss//(010)δ. The composite processing Nb–40Ti–10Si–5Al–2V (at.%) has outstanding toughness (21.62 MPa·m1/2). It has ascertained that the room-temperature fracture toughness of Nb–Si-based in-situ composite is positively impacted by the high concentration of Ti.

A novel electrochemical method for the removal of aluminum from ionic rare earth leachate

The separation of aluminum (Al) from ionic rare earth (RE) leachate is a complex challenge due to their similar chemical properties. Conventional industrial separation process required the use of chemical precipitant leads to considerable loss of RE. Herein, a novel cleaner approach of anionic membrane electrolysis (AME) combined with cyclone electrolysis for removal Al from ionic rare earth leachate was developed. The diffusion of RE3+ and neutralization of H+and OH– were inhibited efficiently by the anionic membrane. Cyclone mixing reduced the loss of rare earth and improved Al removal compared with mechanical mixing. Working parameters including electrode speed, temperature, pH and Al concentration of catholyte, magnesium sulfate concentration and initial pH of anolyte were investigated to explore ways for more efficient Al removal and reduction of rare earth loss. Under the optimal conditions, the removal efficiency of Al and the loss ratio of RE were 93.3 % and 1.84 % respectively. The Al removal data was fitted to the pseudo-zero order model under optimal conditions, k was 0.409 mg·L−1·min−1. Loss of RE was attributed to the direct deposition on the electrode surface due to the high local pH of cathode. This work provides a new insight into the clean removal of Al impurity from actual RE leachate in magnesium sulfate system.

The Influence of Nitrogen Partial Pressure on the Microstructure and Mechanical Properties of HfNbTaTiVZr High-Entropy Nitride Coating Deposited via Direct Current Cathodic Vacuum Arc Deposition

In recent years, high-entropy alloys have attracted increasing scientific interest. Due to their promising combination of properties, such as high hardness and high temperature stability, they are attractive for use as tool coatings for machining applications, to give but one example. Previous studies often focused on layer deposition using magnetron sputtering. Comparatively little research has been carried out to date on coating deposition using direct current cathodic vacuum arc deposition (CAE), with higher achievable rates and almost completely ionized plasmas. The aim of this work is to investigate (HfNbTaTiZr)N-coatings produced by CAE. The nitrogen content was varied and the effects on the coating properties were investigated. Changing the N2/(N2 + Ar) ratio between 0.1 and 1.0 and varying the working pressure in the chamber from 2 Pa to 5 Pa resulted in variations of the nitrogen content of the coatings, ranging from 30 at% to 50 at%. Although different microstructures of the coatings were obtained, there was only a minor influence on the hardness and Young’s modulus.

Effect of additive and subtractive sequence on the distortion of cone-shaped part during hybrid direct energy deposition

Hybrid manufacturing combines additive manufacturing (AM) and subtractive manufacturing processes to achieve simultaneous benefits. Unlike traditional AM, it allows for interleaved subtractive steps, enhancing machining tool access for parts with high aspect ratios. However, optimizing the printing sequence remains as an area of exploration. In this study with two conical shapes, one exhibited a geometrical mismatch at the interface between two printing sections, while the other did not. 3D laser scanning, finite element simulation, and methodical analysis were used to understand this issue. Printing support structure before machining improved dimensional accuracy, with 0.5 mm reduction in distortion achieved, corresponding to 50 % of the final wall thickness. However, the absence of a feedback mechanism to track wall distortion after the additive process resulted in non-uniform wall thickness with a constant depth of cut during the machining operation. This research highlights the importance of process sequencing in hybrid manufacturing for achieving desired geometry.