Search Results (399)

Dot-by-dot Wire and Arc Additive Manufacturing (WAAM) is a promising technique for producing large-scale lattice structures, offering significant benefits in terms of deposition rate and material utilization. This study explores strategies for fabricating bar intersections using the dot-by-dot WAAM technology, focusing on creating robust and predictable structures without requiring parameter modifications or real-time monitoring during the deposition. Two different deposition strategies were proposed, that can be, at least geometrically, applied to a general intersection with multiple bars with different angles. In this work such strategies were only experimentally tested on two-bar intersections, assessing their performance in terms of geometrical accuracy, symmetry, and material efficiency. Strategies which utilize layer-by-layer deposition with multiple overlapping dots, called B here, demonstrated the best results in terms of the geometrical features in the intersection zone, assessed by different metrics obtained through an analysis of pictures, such as low asymmetry and high material volume in the intersection zone. In addition, the findings suggest that removing cooling pauses during the deposition of multiple dots on the same layer slightly improves the joint by minimizing excess material buildup. The proposed approach offers a scalable framework for optimizing intersection deposition, paving the way for improved large-scale metal lattice structure manufacturing. Full article

To address anisotropy challenges in electric arc-based additive manufacturing of Inconel 718 alloy, this study develops a novel wire feeding oscillated double-pulsed gas tungsten arc welding additive manufacturing method (DP-GTA-AM) enabling precise thermal-mass transfer control. Series of crack-free thin-walled Inconel 718 alloy parts were successfully obtained by this proposed approach, and the microstructure and mechanical properties of the parts were thoroughly studied. The results indicate that the microstructure changes from dendrites and cellular crystals in the bottom to equiaxed grains in the midsection and entirely equiaxed crystals in the top, resulting in notable grain refinement. With an average grain size of 61.76 ?m and an average length of 83.31 ?m of large angle grain boundaries, the density of the <001> direction reaches 19.45. The difference in tensile strength and ductility between the horizontal and the vertical directions decreases to 6.3 MPa and 0.38%, which significantly diminishes anisotropy. Fractographic analysis confirms quasi-cleavage failure with homogeneous dimple distribution, demonstrating effective anisotropy mitigation through controlled solidification dynamics. Full article

This study investigates the machining parameters that affect the surface roughness of additively manufactured specimens employing wire arc additive manufacturing (WAAM) using electric arc welding as a heat source. The specimens were prepared using E6013 and E7018 filler rods for layered deposition on a mild steel base plate. For the machining operation, two variable parameters, cutting speed and depth of cut, were selected and coded as high (480 RPM, 0.5 mm depth) and low (310 RPM, 0.25 mm depth) while keeping the feed rate constant. The study employed a 2^k factorial design of experiment (DOE) using Minitab software to assess the impact of parameters and their levels on the output response of surface roughness. Analysis of variance (ANOVA) results show that cutting parameters like cutting speed and their interaction with the depth of cut significantly affect surface quality. The experimental data were also used to develop polynomial model response equations for predicting surface roughness. This study firmly demonstrates the critical role of machining parameters in enhancing the surface quality of low-cost additively manufactured components using an electric arc welding heat source. Full article

The accurate prediction of weld bead geometry is crucial for ensuring the quality and consistency of wire and arc additive manufacturing (WAAM), a specific form of directed energy deposition (DED) that utilizes arc welding. Despite advancements in process control, predicting the shape and dimensions of weld beads remains challenging due to the complex interactions between process parameters and material behavior. This paper addresses this challenge by exploring the application of symmetrical neural networks to enhance the accuracy and reliability of geometric predictions in WAAM. By leveraging advanced machine learning techniques and incorporating the inherent symmetry of the welding process, the proposed models aim to precisely forecast weld bead geometry. The use of neuronal networks and experimental validation demonstrate the potential of symmetrical neural networks to improve prediction precision, contributing to more consistent and optimized WAAM outcomes. Full article

This study investigates the predictive modelling of weld bead geometry in wire arc additive manufacturing (WAAM) through advanced machine learning methods. While WAAM is valued for its ability to produce large, complex metal parts with high deposition rates, precise control of the weld bead remains a critical challenge due to its influence on mechanical properties and dimensional accuracy. To address this problem, this study utilized machine learning approaches—Ridge regression, Lasso regression and Bayesian ridge regression, Random Forest and XGBoost—to predict the key weld bead characteristics, namely height, width and cross-sectional area. A Design of experiments (DOE) was used to systematically vary the welding current and travelling speed, with 3D weld bead geometries captured by laser scanning. Robust data pre-processing, including outlier detection and feature engineering, improved modelling accuracy. Among the models tested, XGBoost provided the highest prediction accuracy, emphasizing its potential for real-time control of WAAM processes. Overall, this study presents a comprehensive framework for predictive modelling and provides valuable insights for process optimization and the further development of intelligent manufacturing systems. Full article

The thermal history of a part deposited via wire arc additive manufacturing (WAAM) and hence its as-built properties can vary significantly depending on the thermal management applied, especially for metallurgically complex materials. Thus, this work aimed to assess the feasibility of processing thin-walled Scalmalloy^® (Al-Mg-Sc-Zr) structures by WAAM while examining the effects of arc energy and heat dissipation on their response to direct age-hardening heat treatment (without solution annealing). As a complement, the geometry, porosity, and processing time of such parts were also analyzed. The walls were built via the cold metal transfer (CMT) deposition process with different arc energy levels in combination with near-immersion active cooling (NIAC) settings (as thermal management solution), as well as with natural cooling (NC), resulting overall in both low surface waviness and porosity levels. Based on hardness testing, the resultant Scalmalloy^® direct-aging response (relative increase in hardness after direct age-hardening from WAAM as-built state) depended more on the arc energy per unit length of deposit applied. In contrast, the other thermal management approaches (NIAC or NC) helped in maintaining Sc in a supersaturated solid solution during deposition. Thus, Scalmalloy^® strengthening was demonstrated as feasibly triggered by means of a post-WAAM direct age-hardening heat treatment solely. Additionally, in comparison with a thermally equivalent (same interpass temperature) condition based on NC, the NIAC technique allowed the achievement of such a positive result on direct-aging response with much shorter WAAM processing times, therefore improving productivity. Full article

In the present study, an attempt was made to build a thin-walled structure consisting of 10 layers using nitinol wire on a titanium substrate via a gas–metal arc welding (GMAW)-based wire-arc additive manufacturing (WAAM) process. A thin-walled structure was fabricated by using nitinol wire on a titanium substrate at the optimized parameters of a wire feed speed of 6 m/min, a travel speed of 12 mm/s, and a voltage of 20 V. In a microstructural study, the heat-affected zone was observed to have coarse grains and be columnar in shape, and the first layer exhibited a mix of dendritic structures. The mid-layers demonstrated a mix of coarse and fine columnar grains with dendritic colonies, while the last few layers demonstrated fairly equiaxed grains as well as a finer microstructure, as the cooling rates were very slow. The ultimate tensile strengths (UTSs) obtained at the bottom and top portions were found to be 536.22 MPa and 586.31 MPa. Elongation (EL) degrees of 10.72% and 11.57% were observed in the bottom and top portions, respectively. The fractography of the tensile specimen showed good toughness and ductility of the fabricated nitinol specimen. A microhardness examination showed a minimum value of 236.56 HV in the bottom layer and a maximum value of 316.78 HV in the topmost layer. Full article

Additive manufacturing (AM) is revolutionizing the fabrication of metallic components, offering significant potential to compete with or complement traditional casting, forging, and machining processes, and enabling the production of complex functional components. Recent advancements in AM technology have facilitated the processing of shape memory alloys (SMAs) with functional properties comparable to those of conventionally processed alloys. However, the AM of NiTi SMAs remains underexplored due to the extreme complexity of the process, high melting point, and reactivity with oxygen. This study investigates the impact of AM processing on the shape memory properties of NiTi alloys using the Micro Wire and Arc Directed Energy Deposition (μ-WA-DED) technique in short circuit mode with a pioneering 0.3 mm pre-alloyed wire, focusing on increasing precision and control in the deposition process. The macroscopic morphology, microstructure, phase composition, phase-transformation temperatures, and mechanical properties of each deposited layer were analyzed. Results indicated austenite (B2) as the predominant phase, with retained martensite (B19′) and a reversible martensitic transformation (B2 ⇌ B19′) in the second layer. Mechanical characterization revealed variations in hardness (H) and elastic modulus (E) due to microstructural heterogeneity and composition. The first layer exhibited H = 3.8 GPa and E = 70 GPa, associated with the B2-NiTi phase, while higher values were obtained in the second layer, i.e., E = 100 GPa and H = 7 GPa. This study establishes for the first time the feasibility of NiTi alloy deposition with a 0.3 mm wire, setting a new standard for future research and applications in AM using μ-WA-DED. Full article

Wire Arc Additive Manufacturing (WAAM) 316L stainless steel unavoidably introduces defects such as porosity, oxide inclusions, and lack of fusion due to the inherent characteristics of the process. These defects can significantly affect the mechanical properties and service reliability of the material. This study focused on evaluating the defects in WAAM 316L stainless steel by nonlinear ultrasonic testing based on Lamb waves. The effects of FCAW (flux cored arc welding) parameters, including shielding gases (98% Ar + 2% O₂ and 100% CO₂) and welding speeds (20, 30, and 40 cm/min), on the columnar grain, porosity, and defect types were systematically analyzed. The formed specimens were then subjected to nonlinear ultrasonic testing, and the results showed that the ultrasonic nonlinear parameters exhibited high sensitivity to changes in porosity. This suggests that nonlinear ultrasonic testing can effectively assess processing defects in WAAM 316L stainless steel. The findings provide valuable insights for optimizing the WAAM process and improving the reliability of additive manufacturing components. Full article

This article presents the results of experimental studies on the dynamic and static strength of commercial aluminum alloy 5056 manufactured by wire-arc additive manufacturing (WAAM). The main objective is to evaluate the utilization potential of this technology for manufacturing parts for operation under shock loads. The dynamic tensile strength of the material was investigated with a modified Kolsky method, implemented by a split Hopkinson pressure bar. A comparative analysis of the strength characteristics of materials manufactured by WAAM and conventional cold-rolling methods was carried out using a structurally temporal approach with the incubation time criterion. The results showed that the aluminum alloy obtained by WAAM demonstrates comparable strength levels to that of cold-rolled material. The findings suggest that WAAM can be a competitive alternative for producing high-strength aluminum alloys for operation under shock loads. Full article

This study examines the microstructure and mechanical properties of 5356 aluminum alloy under low heat input conditions during arc additive manufacturing, focusing on the challenges posed by excessive heat input, which hinders specimen formation and affects dimensional accuracy. The study analyzes the characteristics of single-pass multilayer straight-walled specimens fabricated under varying low heat input conditions, along with evaluations of their mechanical properties, including their microstructure, microhardness, and tensile strength. This study demonstrates that as the heat input increases from 87.5 J/mm to 190.0 J/mm, the width of the vertical wall specimens increases significantly, whereas the change in single-layer height remains minimal. The specimen width increases from 5.22 mm to 8.87 mm, representing a change of 3.65 mm, while the single-layer height increases by only 0.16 mm. The microstructure primarily consists of the α(Al) matrix and the skeletal β(Al₃Mg₂) phase. As heat input increases, some of the β(Al₃Mg₂) phase dissolves, resulting in a decrease in its distribution density, a reduction in its quantity, and an increase in its size. The average hardness increases from 69.40 HV at 87.5 J/mm to 77.89 HV at 154.2 J/mm, before decreasing to 73.56 HV at 190.0 J/mm. As the heat input increases, the tensile strength and elongation of both horizontal and vertical specimens initially increase and then decrease. The tensile strength and elongation of the horizontal specimens are slightly greater than those of the vertical specimens. The microstructure and mechanical properties vary across different regions. In the upper region, the β(Al₃Mg₂) phase is uniformly distributed, with high density and small size. The fracture surface exhibits fine, uniform dimples, displaying the best microhardness and mechanical properties, with a tensile strength of 245.88 MPa. In the middle region, the distribution density of the β phase decreases, the size increases, and the dimples become slightly coarser. Consequently, the microhardness and mechanical properties decline. At the bottom, due to the higher cooling rates, the β phase does not dissolve significantly. The distribution density is high, the dimples are large and uneven, and the microhardness and mechanical properties are the lowest, with a tensile strength of 236.00 MPa. Full article

Wire Arc Additive Manufacturing (WAAM) is a process for fabricating metal parts known for its high productivity and material flexibility. However, defects such as overheating, residual stresses, distortions, porosity, and a non-homogeneous microstructure limit its commercial applications. Therefore, the present study aims to analyze the correlation between electrical sensing anomalies in the Gas Metal Arc (GMA) during WAAM and the occurrence of microscopic defects caused by external contamination. To achieve this, experiments were conducted to fabricate walls using WAAM with controlled contaminant introduction. Simultaneously, electrical arc data, specifically voltage and current, were segmented and acquired during the wall deposition process. Metallographic analysis confirmed the presence of microscopic defects or changes in the solidification patterns in regions with contaminant inclusion, distinguishing them from other areas of the analyzed samples. Similarly, the contaminations were proven to cause anomalies in attributes associated with the electrical arc. Therefore, this approach confirms the criticality of electrical arc monitoring in WAAM, as it demonstrates that anomalies in the electrical arc could lead to microstructural consequences. Full article

Freedom of design and the cost-effective production of structural parts have led to much research interest in Wire Arc Additive Manufacturing (WAAM). Nevertheless, WAAM is subject to design constraints and fundamentally differs from other additive manufacturing processes. Consequently, design guidelines and supporting design evaluation tools adapted to WAAM are needed. One geometric approach to design evaluation is the use of a three-dimensional medial axis transformation (3D-MAT) to derive local geometry indicators. Previous works define the thickness and radius indicators. In this work, the angle between opposing faces and a mass gradient indicator are added. To apply the literature design rules regarding wall thickness, clearance, bead angle, and edge radius to specific geometry regions, features are classified by the indicators. Following a literature suggestion, wall and corner regions are differentiated by the angle indicator. An angle of ${65}^{°}$ is identified as an effective separation limit. Additionally, the analogy of Heuvers’ spheres to the MAT helps estimate a limit of ${\displaystyle \frac{k_H-1}{k_H+1}}$ for the mass gradient ($k_H$: Heuvers’ factor). Finally, tests on example parts demonstrate the method’s effectiveness in verifying compliance to the specified rules. With a numerical complexity of $\mathcal{O}\left(n^2\right)$, this method is more efficient than finite element analyses, providing early feedback in the design process. Full article

The microstructure, texture, and mechanical properties of Inconel 718 fabricated via hybrid wire-arc additive manufacturing (WAAM) with inter-pass forging, and the subsequent modified post-deposition heat treatment (PDHT), were investigated. The modified PDHT included homogenization at 1185 °C and double ageing at 720 °C, with furnace-cooling to 620 °C; this process was first used for Inconel 718 obtained via WAAM and inter-pass forging. In the as-printed material, two characteristic zones were distinguished, as follows: (i) columnar grains with a preferable <100> orientation and (ii) fine grains with a random crystallographic orientation. The development of static recrystallization induced via inter-pass forging and further heating during the deposition of the next (upper) layer provoked the formation of the fine-grained zone. In the as-printed material, particles of (Nb,Ti)C and TiN, and precipitates of a Nb-rich Laves phase that caused premature cracking and failure during mechanical testing, were detected. In the PDHT material, two zones were found, as follows: (i) a zone with coarse uniaxial grains and (ii) a zone with a gradient grain size distribution. PDHT resulted in the precipitation of γ″ nanoparticles in the γ-Ni matrix and the dissolution of the brittle Laves phase. Therefore, significant hardening and strengthening, as well as increases in ductility and impact toughness, occurred. Full article

Additive manufacturing (AM) has evolved to enable the direct production of functional components through the hybridization of additive and subtractive processes. In metal wire AM, hybridization is key, encompassing process integration (addition/subtraction), energy source combinations (arc/laser), kinematic options (3/4/5 axis), and slicing techniques (planar/conformal). This paper focuses on these hybridization methods, with a unified system designed for single-machine setups, improving efficiency and accuracy. This study presents a detailed exploration of these hybridization levels through the fabrication of a complex 5-axis geometry—an impeller. The impeller was manufactured with hybridization using various levels and subsequently compared with manufacturing processes like additive manufacturing with interlayer machining and traditional machining methods. The hybrid approach significantly reduced the manufacturing time for the selected impeller geometry from 3536 min to 792 min (saving 77.6% manufacturing time) and minimized material waste to 9.3%, compared with 74.07% in traditional machining. This demonstrates a more efficient, precise, and cost-effective method to optimize metal wire AM for producing complex metal components, advancing capabilities and applications. Full article