High Deposition Rate Research Articles

Assessment on wire-arc additive manufactured high strength low alloy steel cylindrical component

Large structural parts are widely manufactured through wire-arc additive manufacturing (WAAM) due to its high deposition rate, flexibility, and low cost. There are a variety of industries where high strength low alloy (HSLA) steel is used, including naval, tool and die manufacturing, construction, and offshore structures. The present article examines the mechanical properties and microstructural evolution of a developed HSLA component. The microstructural analysis was done in the component’s top (TR) and bottom (BR) regions. It reveals almost similar microstructural constituents but with more polygonal ferrite in the TR and bainitic structure in the bottom, with acicular ferrite in both regions. The inclusions in both regions were characterized using energy-dispersive X-ray spectroscopy. This demonstrates that manganese (Mn), as a strong deoxidizer, reacts with oxygen and dissolves entirely within the inclusion, forming a Mn depletion zone. Additionally, grain coarsening was observed in the building direction. The average grain size in the TR and BR was 13.12 μm and 6.54 μm, respectively. Within the regions considered, only 2.47%, 4.06%, and 0.65% variations were observed between yield strength, ultimate tensile strength, and elongation to fracture.

A Comprehensive Review and Future Perspectives of Simulation Approaches in Wire Arc Additive Manufacturing (WAAM)

Abstract Wire arc additive manufacturing (WAAM) has emerged as a promising technique for producing large-scale metal components, favoured by high deposition rates, flexibility and low cost. Despite its potential, the complexity of WAAM processes, which involves intricate thermal dynamics, phase transitions, and metallurgical, mechanical, and chemical interactions, presents considerable challenges in final product qualities. Simulation technologies in WAAM have proven invaluable, providing accurate predictions in key areas such as material properties, defect identification, deposit morphology, and residual stress. These predictions play a critical role in optimizing manufacturing strategies for the final product. This paper provides a comprehensive review of the simulation techniques applied in WAAM, tracing developments from 2013 to 2023. Initially, it analyzes the current challenges faced by simulation methods in three main areas. Subsequently, the review explores the current modelling approaches and the applications of these simulations. Following this, the paper discusses the present state of WAAM simulation, identifying specific issues inherent to WAAM simulation itself. Finally, through a thorough review of existing literature and related analysis, the paper offers future perspectives on potential advancements in WAAM simulation strategies.

Free‐Radical Polymerization of Liquid Hydroxyethyl Methacrylate Layers Using Nanosecond Plasma Pulses

ABSTRACTPromoting both high functional group preservation and high deposition rates is a major challenge in plasma deposition. This study explores a dynamic method using nanosecond pulsed plasma discharges to polymerize thin liquid layers of 2‐hydroxyethyl methacrylate (HEMA). The influence of plasma pulse frequency (200 ns) and liquid layer thickness on chemical structure retention, polymeric growth, and thin film growth rate is examined. High‐resolution mass spectrometry (HRMS) highlights that plasma curing of liquid monomer layers achieves significantly better chemical structure preservation and polymeric growth, along with deposition rates an order of magnitude higher than traditional vapour‐phase methods. This work provides valuable insights and guidelines for plasma‐induced free‐radical polymerization of liquid layers into functional thin solid films.

Tribological performance of 410L martensitic stainless steel parts manufactured by Laser directed energy deposition

The processing of AISI 410L martensitic stainless steel (MSS) by laser directed energy deposition (L-DED) for additive manufacturing (AM) of wear-resistant components is an alternative to the high C-content MSS grade, with difficult processability. This work assesses the tribological performance of low C-content 410L MSS additively manufactured by L-DED. Two sets of L-DED parameters were investigated, one targeting Production and high deposition rates, and the other for Resolution and increased geometric freedom. Half of the multilayer samples were subjected to a post heat-treatment route. Samples were evaluated by the dry-sliding linearly reciprocating ball-on-flat tribological test (ASTM G133) in the as-built and heat-treated states. Commercially annealed 410 MSS was the reference material. In the L-DED as-built, microstructures were composed of ferrite with martensite at the grain boundaries. Heat-treatment provides recrystallization, martensite tempering, and hardness decrease. The more refined microstructure of L-DED resolution as-built led to greater hardness and lower wear coefficient in the ASTM G133 test. Wear tracks revealed wider bands of compact tribolayers on its surface, which reduced the action of adhesive and abrasive mechanisms. The other L-DED as-built and heat-treated conditions, and 410 reference material demonstrated a large amount of free debris, indicating lower wear resistance.

Systematic Review on Additive Friction Stir Deposition: Materials, Processes, Monitoring and Modelling

Emerging solid-state additive manufacturing (AM) technologies have recently garnered significant interest because they can prevent the defects that other metal AM processes may have due to sintering or melting. Additive friction stir deposition (AFSD), also known as MELD, is a solid-state AM technology that utilises bar feedstocks as the input material and frictional–deformational heat as the energy source. AFSD offers high deposition rates and is a promising technique for achieving defect-free material properties like wrought aluminium, magnesium, steel, and titanium alloys. While it offers benefits in terms of productivity and material properties, its low technology readiness level prevents widespread adoption. Academics and engineers are conducting research across various subfields to better understand the process parameters, material properties, process monitoring, and modelling of the AFSD technology. Yet, it is also crucial to compile and compare the research findings from past studies on this new technology to gain a comprehensive understanding and pinpoint future research paths. This paper aims to present a comprehensive review of AFSD focusing on process parameters, material properties, monitoring, and modelling. In addition to examining data from existing studies, this paper identifies areas where research is lacking and suggests paths for future research efforts.

Numerical simulation and experimental analysis of aerosol deposition: Investigating nozzle effects on particle dynamics and deposition

Aerosol deposition (AD), also known as vacuum kinetic spray (VKS), is used to deposit dense ceramic films onto a substrate surface at room temperature. One predominant factor influencing the overall deposition process is the nozzle geometry, which significantly impacts the quality, shape, and thickness of the coating. To evaluate the effect of nozzle geometry in AD, particle trajectory and impact velocity were investigated via computational simulation. A Eulerian-Lagrangian model was used to simulate the gas flow, particle in-flight behavior, as well as particle deposition characteristics on a flat substrate. Three common nozzle geometries in AD were utilized: a converging-diverging nozzle with a slit cross-section (CD-Slit), a converging-barrel nozzle with a slit cross-section (CB-Slit), and a converging-diverging round (CD-Round) nozzle. Moreover, suitable drag coefficient and Nusselt number correlations were used to account for compressibility and rarefaction effects on particle dynamics and heat transfer. The simulation results were compared to the deposition pattern obtained experimentally. The results demonstrate that shape of the nozzle has profound effect on the particle impact velocity and deposition pattern. The CD-Round nozzle provides uniform, thinner coatings ideal for extensive surfaces at a slower deposition rate. In contrast, the CB-Slit nozzle is optimized for maximum coating thickness in narrow, thick linear patterns. The CD-Slit nozzle achieves high deposition rates with uniform coatings and a distinctive cat-ear shaped pattern.

Indium oxide buffer layer for perovskite/Si 4-terminal tandem solar cells with efficiency exceeding 30%

Perovskite/Si tandem solar cells (TSCs) present great potential to surpass the Shockley-Queisser limit of single-junction solar cells for further advancing the power conversion efficiency (PCE) of solar cells. However, the fabrication of TSCs usually encounters challenge of selecting suitable sputtering buffer layer (SBL) to prevent the bombardment during the transparent electrode deposition. Herein, we introduce an indium oxide (In2O3) buffer layer via e-beam deposition to fabricate semi-transparent perovskite solar cells (ST-PSCs). The optical transmittance and electrical conductivity of In2O3 highly depend on the deposition rate. High deposition rate results in high ratio of metallic indium in the film, which causes severe parasitic absorption. A 20 nm-thick In2O3 film deposited at lower rate demonstrated high conductivity, transmittance and robust protection during sputtering. A 1.68 eV ST-PSC incorporating this In2O3 buffer layer exhibits a champion PCE of 20.20%, demonstrating the excellent optoelectronic and protective properties of In2O3. When combined with a Si subcell, the 4-terminal TSC obtains a remarkable PCE of 30.04%. Importantly, the unencapsulated ST-PSC maintained 80% of initial PCE after 423 h of continuous light soaking in N2. This work has provided a facile and instrumental transparent SBL strategy for perovskite/Si TSCs.

PARMS coating technology for UV to IR laser applications

AbstractReactive sputtering using a medium frequency (MF) dual magnetron source is an advanced technique widely employed in various thin film deposition applications. For the production of high‐quality optical filters based on oxides with low losses, it is crucial to exclude any form of arcing, including both strong arcs and microarcs. These requirements are solved by plasmaassisted reactive magnetron sputtering (PARMS), which also provides a high deposition rate contributing to the economically efficient production of high‐end optical filters.

Large eddy simulation of droplet dispersion and deposition over street canyons

Predicting droplet transport in the atmosphere is a major issue for a large number of dispersion problems such as spray cooling systems in streets, urban lawn sprinklers [Milesi et al., “Interferometric laser imaging for respiratory droplets sizing,” Environ. Manage. 36, 426–438 (2005)], and dispersion of virus such as COVID or from a terrorist attack [Balachandar et al., “Host-to-host airborne transmission as a multiphase flow problem for science-based social guidelines,” Int. J. Multiphase Flow 132, 103439 (2020)]. Here, we investigate the propagation of droplets issued from a source near the ground between square obstacles with different spacings. The aerodynamic field is determined by large eddy simulation coupled with an immersed boundary method for the obstacles. Droplets are tracked by a Lagrangian approach. An evaporation model is used to account for varying humidity conditions. Droplet concentration, mass flux, and deposition rates are obtained for different evaporation conditions and obstacle spacings. The results show high deposition rates on the internal wall of the first obstacle due to droplet advection by the reverse flow of the primary vortex. In addition to this, droplets may escape the canyon and propagate downstream as far as eight times the obstacle distance (8H). The concentration of air-borne droplets downstream the canyon is higher for smaller street canyon openings. When evaporation is accounted for, the ground-level droplet concentration may be reduced by up to 30% in the case of small canyon openings.

Machine Vision to Provide Quantitative Analysis of Meltpool Stability for a Coaxial Wire Directed Energy Deposition Process.

Wire-based additive manufacturing (AM) is at the forefront of complex metal fabrication because of its scalability for large components, potential for high deposition rates, and ease of use. A common goal of wire directed energy deposition (DED) is preserving a stable process throughout deposition. If too little energy is put into the deposition, the wire will stub into the substrate and begin oscillating, creating turbulence within the meltpool. If too much energy exists, the wire will overheat, causing surface tension to take over and create liquid drips as opposed to a solid bead. This paper proposes a computer vision technique to work as both a state detection and event detection system for wire stability. The model utilizes intensity variations along with frame-to-frame difference calculations to determine process stability. Because the proposed model does not rely on machine learning techniques, it is possible for an individual to interpret and adjust as they see fit. The first part of this paper describes creation and implementation of the model. The model's capability was then evaluated using a 1D laser power experiment, which generated a wide range of stability states across varying powers. The model's accuracy was evaluated through 3D geometry data gathered from the experimentally deposited beads. The model proved to be both capable and accurate and has potential to be used as a real-time control system with future work.

Experimental study on the heat input behavior of wire-arc additively manufactured 316L stainless steel parts for repairing applications

Wire arc additive manufacturing (WAAM) as an emerging manufacturing technique for fabricating large size metallic components with a higher deposition rate and lower material wastage. In this research, a thin walled-part was fabricated from stainless steel 316L with various heat input (HI) (low heat deposited wall (LHDW) and high heat deposited wall (HHDW) using the cold metal transfer (CMT)-based WAAM process. The microstructure characteristics, metallurgical characterization, and mechanical properties of the WAAM manufactured thin-walled component were examined. The deposited wall measuring 120 mm in length and 50 mm in height was fabricated by WAAM using ER316L wire and CMT. Microstructure of the deposit parts consists of the equiaxed, coarse, and columnar grains with epitaxial growth of dendrites were formed. The decrease in HI leads to the improvement of material hardness, yield and ultimate tensile strength (UTS) as well as the percentage elongation after fracture of the material decreases. EBSD analysis demonstrates the average grain size of 0.98 µm in LHDW and 2.43 in HHDW respectively. XRD results shows that main crystal structure found in WAAM thin-walled sample was γ-austenite phases. The microhardness distribution of the fabricated component exhibited the stability characteristics with the average value ranging between 213–237 HV. The tensile studies demonstrate the UTS of the LHDW and HHDW along the horizontal direction are 477 MPa greater than the vertical direction of 468 MPa and observed the anisotropy properties. The fractured surface was characterized by the emergence of obvious dimples revealing the ductile fracture. The lower HI and finer solidification structure of component fabricated by LHDW has greater tensile and hardness properties than that of HHDW. This study presents the initial assessment results for repairing stainless steel components subjected to mechanical damage.

Temporal and Spatial Variations in Microplastic Concentrations in Small Headwater Basins in the Southern Blue Ridge Mountains, North Carolina, USA

Microplastics (MPs) are ubiquitous contaminants of emerging concern that require additional study in freshwater streams. We examined the spatial-temporal variations in MP concentrations and characteristics within two headwater basins in the Southern Appalachian Mountains of western North Carolina over ~1 year. Atmospheric samples were also collected to determine the significance of atmospheric MP deposition to these relatively small streams. MP concentrations in both basins were within the upper quartile of those reported globally, reaching maximum values of 65.1 MPs/L. Approximately 90% of MPs were fibers. MP composition was dominated by polystyrene, polyamides, and polyethylene terephthalate. Spatially, concentrations were highly variable and increased with development, indicating anthropogenic inputs from urbanized areas. MP concentrations were also elevated in forested tributary subbasins with limited anthropogenic activity, suggesting atmospheric deposition was an important MPs source. Significant atmospheric inputs are supported by high atmospheric depositional rates (ranging between 7.6 and 449.8 MPs/m2/day across our study sites) and similarities in morphology, color, and composition between atmospheric and water samples. Temporally, MP concentrations during storm events increased, decreased, or remained the same in comparison to base flows, depending on the site. The observed spatial and temporal variations in concentrations appear to be related to the complex interplay between precipitation and runoff intensities, channel transport characteristics, and MP source locations and contributions.

Influence of parameter variation and interlayer temperature control in wall angle, curvature and measurement methodology of ER70S-6 parts obtained by WAAM

Wire and Arc Additive Manufacturing is characterized for the high deposition rates, enabling the manufacturing of big, complex parts, with smaller relative production cost. However, once the part receives high heat inputs, leading to geometry variation and deformations, it is important to properly measure the part characteristics. Therefore, this work contributes with a measurement methodology for inclined walls deposited by Wire and Arc Additive Manufacturing and its application on walls deposited with different parameters. The main parameter of influence was the use of interlayer temperature control, which increased the angle in 71.0%, and the curvature in 90.3%, lower part.

A review on aluminum alloys produced by wire arc additive manufacturing (WAAM): Applications, benefits, challenges and future trends

Metal additive manufacturing is advancing with increasing momentum and attracting great attention. The Wire Arc Additive Manufacturing (WAAM) process, one of the metal additive manufacturing methods, involves melting a filler wire with an electric arc and depositing metal droplets layer by layer along the planned path. Aluminum alloys produced by the WAAM process have been in high demand in the industry, especially in the last decade. The WAAM process stands out as a suitable method for many industries due to its low investment cost, high deposition rates and the advantages of creating relatively complex parts. Key application areas of aluminum alloys produced using WAAM include aerospace, automotive, marine, and energy sectors, where lightweight structures, corrosion resistance, and high strength are critical. Much research has been done and innovative applications, including hybrid systems, have been developed to prevent defects such as residual stresses, cracks, porosity and delamination. This review article provides a comprehensive overview of the use of the WAAM process in aluminum alloys over the past decade. In the article, firstly, aluminum alloys, the WAAM technique and its types are introduced. In the following section, the methods used to improve mechanical properties and optimize the microstructure are examined in detail. In the next section, the difficulties encountered when using aluminum alloys in WAAM applications are discussed in detail. In the discussion section, current developments are evaluated, and in the last section, suggestions for future studies and inferences obtained from this study are presented. As a result, WAAM-CMT and hybrid systems were found to be effective in reducing defects such as porosity, distortion and residual stress. In addition, post-processing heat treatments and surface treatment methods are also crucial for improving mechanical properties. Finally, more research is needed in the areas of 7xxx series alloys, repair applications and environmental sustainability.

Life cycle assessment in additive manufacturing of copper alloys—comparison between laser and electron beam

Additive manufacturing is becoming increasingly important for industrial production. In this context, directed energy deposition processes are in demand to achieve high deposition rates. In addition to the well-known laser-based processes, the electron beam has also reached industrial market maturity. The wire electron beam additive manufacturing offers advantages in the processing of copper materials, for example. In the literature, the higher energy efficiency and the resulting improvement in the carbon footprint of the electron beam are highlighted. However, there is a lack of practical studies with measurement data to quantify the potential of the technology. In this work, a comparative life cycle assessment between wire electron beam additive manufacturing (DED-EB) and laser powder additive manufacturing (DED-LB) is carried out. This involves determining the resources for manufacturing, producing a test component using both processes, and measuring the entire energy consumption. The environmental impact is then estimated using the factors global warming potential (GWP100), photochemical ozone creation potential (POCP), acidification potential (AP), and eutrophication potential (EP). It can be seen that wire electron beam additive manufacturing is characterized by a significantly lower energy requirement. In addition, the use of wire ensures greater resource efficiency, which leads to overall better life cycle assessment results.

Additive manufacturing between cooled confinements with the LDNA process

Laser-assisted double-wire welding with nontransferred arc (LDNA) is characterized by two converging wires between which an electrical arc burns to melt both wires. The molten material falling onto the substrate is distributed with oscillating laser radiation with a power of 1.5 kW to ensure sufficient bonding with the substrate without delamination and pores. The process is characterized by high deposition rates of more than 7.5 kg/h. Due to the high deposition rate, only high values for waviness in the buildup direction can be achieved in the production of multilayer additive structures. The approach investigated in this publication examines the potential to produce additive structures with a confined melt pool. The use of water-cooled copper jaws and the deposition of ER70S-6 between these confinements using the LDNA process are being investigated to produce additive 10 mm wide and 100 mm long structures with significantly improved waviness in the direction of buildup and improved dimensional accuracy. It can be shown that a wall-like structure can be welded between the confinements without material bonding to the cooling jaws. Additionally, it has been observed that the confinements can easily be removed which is attributed to the thermal contraction of the steel. Metallographic examinations of the produced structures in the longitudinal and transverse sections as well as hardness curves in the transverse section are carried out and evaluated. Multilayer structures with up to five layers are produced and the waviness and surface roughness on the side surfaces defined by the jaws are measured and evaluated.

Investigating the impact toughness properties and influential factors of titanium alloy joints

Double-sided symmetric MIG welding can significantly enhance welding efficiency for thick titanium alloys and holds promising engineering applications. However, the use of high currents and deposition rates in this process not only boosts welding efficiency but also impacts joint performance, particularly its impact toughness. In this study, the Charpy impact performance of double-sided double-arc MIG welded joints in each region was studied via oscillometric impact tests, and the main factors affecting the impact of joints were revealed. Scanning electron microscope was used to observe the fractures, and the microstructure characteristics and grain orientation of the impact crack propagation path were observed and analysed via metallurgical microscopy and EBSD. In addition, the microstructure of each region of the joint was observed via metallographic microscopy and transmission electron microscopy, which revealed the microstructure characteristics of different regions of the joint and clarified the effects of microstructure and grain orientation in different regions of the welded joint on the impact performance of each region of the double-sided, double-arc MIG welded joint. The results show that the crack initiation energy across different regions of joints typically ranges between 18 and 20 J, with minimal variations. Crack propagation plays a pivotal role in determining impact toughness, which is influenced both by microstructural features and orientation. This provides guidance for subsequent adjustments and improvements to the impact performance of the joint.

Impact of piezoelectric driving waveform on performance characteristics of vibrating mesh atomizer (VMA)

Vibrating mesh atomizer (VMA) is a specific type of ultrasonic atomizer known for its low power consumption and production of uniformly fine droplets. While previous research has provided a basic understanding of VMA operation, it has primarily focused on driving the piezoelectric actuator with continuous and symmetrical waveforms, such as sine and square waveforms. This study aims to experimentally investigate the impact of different driving waveforms on the ultrasonic atomization process and the associated performance characteristics. Specifically, the effects of pulse waveforms (Gauss and Lorentz pulse) were analyzed with high rates of energy deposition and asymmetrical hybrid waveforms (trapezia and absolute sine), featuring distinct negative cycles, by comparing them with conventional symmetrical waveforms (sine and square). Pulse waveforms suppress the growing stage but provide a high flux of input energy, facilitating the detachment of liquid into fine droplets, resulting in uniformly distributed droplets with VMDs of 5.84 μm and 4.71 μm for Gauss and Lorentz waveforms, respectively. Conversely, shorter negative cycles in asymmetrical hybrid waveforms reduce liquid suction into the micronozzle, leading to higher energy flux during subsequent positive cycles that promote the growing stage, producing larger droplets with VMDs of 10.82 μm and 11.86 μm for trapezia and absolute (abs) sine waveforms, respectively. Additionally, high-speed imaging reveals irregular pulsating behaviors in the atomization process when using pulse waveforms, suggesting a reciprocating-pump-like operation mechanism in VMA atomization. These new insights contribute to an improved understanding of the atomization mechanism in VMAs.

An Investigation of Thermomechanical Behavior in Laser Hot Wire Directed Energy Deposition of NAB: Finite Element Analysis and Experimental Validation

Laser Hot Wire (LHW) Directed Energy Deposition (DED) Additive Manufacturing (AM) processes are capable of manufacturing parts with a high deposition rate. There is a growing research interest in replacing large cast Nickel Aluminum Bronze (NAB) components using LHW DED processes for maritime applications. Understanding thermomechanical behavior during LHW DED of NAB is a critical step towards the production of high-quality NAB parts with desired performance and properties. In this paper, finite element simulations are first used to predict the thermomechanical time histories during LHW DED of NAB test coupons with an increasing geometric complexity, including single-layer and multilayer depositions. Simulation results are experimentally validated through in situ measurements of temperatures at multiple locations in the substrate as well as displacement at the free end of the substrate during and immediately following the deposition process. The results in this paper demonstrate that the finite element predictions have good agreement with the experimental measurements of both temperature and distortion history. The maximum prediction error for temperature is 5% for single-layer samples and 6% for multilayer samples, while the distortion prediction error is about 12% for single-layer samples and less than 4% for multilayer samples. In addition, this study shows the effectiveness of including a stress relaxation temperature at 500 °C during FE modeling to allow for better prediction of the low cross-layer accumulation of distortion in multilayer deposition of NAB.

Integration of Multifunctionality in a Colloidal Self‐Repairing Catalyst for Alkaline Water Electrolysis to Achieve High Activity and Durability

Self‐repairing catalysts are useful for achieving alkaline water electrolyzers with long lifetimes under intermittent operation. However, rational methodologies for designing self‐repairing catalysts have not yet been established. Herein, hybrid cobalt hydroxide nanosheets (Co‐ns), with a high deposition (repairing) rate, and β‐FeOOH nanorods (Fe‐nr), with high oxygen evolution reaction (OER) ability, are electrostatically self‐assembled into composite catalysts. This strategy is developed to integrate multifunctionality in self‐repairing catalysts. Positively charged Co‐ns and negatively charged Fe‐nr form uniform composites when dispersed in an electrolyte. These composites are electrochemically deposited on a nickel electrode by electrolysis at 800 mA cm−2. Co‐ns form a conductive mesoporous assembly of CoOOH nanosheets as a support. Fe‐nr are then distributed on the CoOOH nanosheets as active sites for the OER. Because of the high deposition rate of Co‐ns, the amount of Fe‐nr deposited increases 22 times compared to when Fe‐nr is deposited alone, and the OER current density increases 14 times compared to that of Co‐ns alone. The composite self‐repair catalyst shows the highest activity and durability under an accelerated durability test (ADT), and its degradation rate decreases from 84 μV cycle−1 (Fe‐nr only) to 60 μV cycle−1 (composite catalyst) under ADT conditions without repair.