Wire And Arc Additive Manufacturing Research Articles

ESTRATEGIAS DE DEPOSICIÓN Y PROGRAMACIÓN PARA ABORDAR LA FABRICACIÓN DE PIEZAS DE GEOMETRÍA COMPLEJA MEDIANTE WAAM (WIRE AND ARC ADDITIVE MANUFACTURING)

This work analyzes the factors that affect the manufacture of complex geometry parts by WAAM (Wire and arc additive manufacturing) with the aim of minimizing the material used, improving the Buy-to-Fly ratio (ratio of raw material weight divided by the weight of the final component) and avoiding part distortions. A study of the different material deposition strategies to manufacture the parts (straight beads, circular path beads, serpentine, overlapping beads...) has been carried out to obtain the desired geometry. Depending on the deposition strategy to be used and the geometry of the part, the best option for the definition of robot trajectories has been analyzed, which can be done by direct programming of the robot or in a CAD-CAM design environment. Another aspect to be considered in manufacturing is the time between layers. This time affects the growth of the parts, since the accumulated heat can cause the growth to be inconsistent and generate distortions. To see the effects of different waiting times, simulation tools have been used. Finally, in order to control the deviations of the real part with respect to the theoretical one, the option of using profilometry has been analysed. This paper aims to analyse the development of new methodologies that respond to the different challenges mentioned above.) Keywords: WAAM, Buy-to-Fly, deposition strategies, robot trajectories, simulation

Grain refinement of Inconel 625 during wire-based directed energy deposition additive manufacturing by in-situ added TiB2 particles: Process development, microstructure evolution and mechanical characterization

In this study, a novel method for enhancing the quality of components fabricated by wire and arc additive manufacturing (WAAM) was developed. This approach employs an innovative mechanism featuring an actuator that dispenses a solution containing refinement particles (TiB2 inoculants), in conjunction with a soldering flux that vaporizes prior to reaching the electric arc. This leaves the particles to adhere to the welding wire or be carried by the shielding gas. By implementing this device, TiB2 particles were successfully incorporated into the molten pool during the WAAM process of Inconel 625 at levels of 0.31 and 0.56 wt%. Microstructural analysis reveals a significant reduction in the size of interdendritic segregation regions when TiB2 particles are introduced. Electron backscatter diffraction analysis further reveals the transformation of columnar grains into equiaxed grains. The average grain area decreased from 1823 μm2 in the as-built sample to 583 μm2 in the sample with a TiB2 content of 0.56 wt%. In addition, an improvement in the Inconel 625 fabricated by WAAM mechanical strength was observed due to the use of TiB2 inoculants, which was primarily attributed to the effect of the grain size refinement.

On the formation of oxide inclusions in the high nitrogen chromium-manganese steel produced by the Wire and Arc Additive Manufacturing

Oxide inclusions significantly impeded the mechanical properties of the Wire and Arc Additive Manufacturing (WAAM) made high nitrogen Cr–Mn austenite stainless steels (HNSs). This paper focused on the inclusions' component, crystallization characteristics and formation mechanism. Results revealed that there are two types of inclusions: the round-shape nano-size inclusion (Type-I) and the micron-size island-shape inclusion (Type-II). The Type-I inclusion usually consists of the MnO particle or the combination of the MnO, Si-oxides and precipitations (MnS or Cr2N). Most of the Type-I oxide inclusion is located in the range between 300 nm and 700 nm,the number of Type-I oxide inclusion takes the main part of 69.7%.With higher content, smaller size and more even distributions, the isolated Type-I oxide inclusions would be beneficial to the mechanical properties owing to the Orowan strengthening mechanism. The Type-II inclusion is mostly composed of the MnO matrix and the coherent chromite spinel (MnCr2O4). In general, the larger the size, the more serious the negative impact on mechanical properties. And there was a strong negative correlation between the size and quantity of type II oxide inclusions. After heat treatment, abundant phase transformations occurred in the Type-II inclusions and some harmful phases (Sigma, MnS et cl.) were often found in or around the inclusions with specific orientation relationships. During deposition, the unstable droplet transformation and the trapped residual slag were the main causes for the inclusions in the molten pool.

Numerical simulation of thermal and stress fields for multilayer and multi-pass weaving WAAM of magnesium alloy

Purpose A 3D finite element (FE) model based on the double ellipsoidal heat source was developed to investigate the evolution of temperature and stress fields during the multilayer and multi-pass wire and arc additive manufacturing (WAAM) process. This paper aims to investigate the evolution of temperature and stress fields during the multilayer and multi-pass wire and arc additive manufacturing (WAAM) process by developing a 3D finite element (FE) model based on the double ellipsoidal heat source. Design/methodology/approach Experimental thermal cycle curves and residual stresses were obtained by thermocouples and X-ray diffraction, respectively. The validity of the model was verified by the corresponding experimental results. Findings The deposition process of the upper pass led to the partial remelting of the lower deposited pass. The thermal process of the current-deposited pass alleviated the stress concentration in the previous-formed passes. A more uniform temperature distribution could be obtained by using the reciprocating deposition path. Compared to the reciprocating deposition path, the peak values of the transverse and longitudinal tensile residual stresses of the deposited sample under the unidirectional deposition path were reduced by 15 MPa and increased by 13 MPa, respectively. The heat conduction in the deposited passes could be improved by extending the inter-pass cooling time appropriately. With an increase in the inter-pass cooling time, the longitudinal residual stress in the middle region of sample along longitudinal and transverse directions showed increase and decrease–increase trends, respectively, while the transverse residual stress exhibited decrease trend. Originality/value This study enhances the understanding of temperature and stress fields evolution during the multilayer and multi-pass cold metal transfer-WAAM processes of magnesium alloy and provides the reference for parameter optimization.

Space–time topology optimization for anisotropic materials in wire and arc additive manufacturing

Wire and Arc Additive Manufacturing (WAAM) has great potential for efficiently producing large metallic components. However, like other additive manufacturing techniques, materials processed by WAAM exhibit anisotropic properties. Assuming isotropic material properties in design optimization thus leads to less efficient material utilization. Instead of viewing WAAM-induced material anisotropy as a limitation, we consider it an opportunity to improve structural performance. This requires the integration of process planning into structural design. In this paper, we propose a novel method to utilize material anisotropy to enhance the performance of structures both during fabrication and in their use. Our approach is based on space–time topology optimization, which simultaneously optimizes the structural layout and the fabrication sequence. To model material anisotropy in space–time topology optimization, we derive the material deposition direction from the gradient of the pseudo-time field, which encodes the fabrication sequence. Numerical results demonstrate that leveraging material anisotropy effectively improves the performance of intermediate structures during fabrication as well as the overall structure.

Prediction and optimization of surface waviness of WAAM components using a hybrid Rank-Gaussian PSO algorithm and ANN

Surface waviness is crucial for the quality of components produced via the wire and arc additive manufacturing (WAAM) process. This study presents a novel method for predicting surface waviness, employing an advanced model to optimize process parameter configurations using a combination of Rank-Gaussian particle swarm optimization (RGPSO) and an Artificial Neural Network (ANN). The novelty of this process is that the RGPSO not only optimizes the hyperparameters of the ANN model to enhance prediction performance, but also addresses surface waviness optimization. The RGPSO algorithm's optimization performance is evaluated using 23 benchmark functions, demonstrating competitiveness against nine comparative meta-heuristic algorithms. Experimental data on surface waviness from the literature are utilized to train, test and validate three different prediction models, including a standalone ANN model, a PSO optimized ANN (PSO-ANN) model, and an RGPSO optimized ANN (RGPSO-ANN) model. The results indicate that the developed RGPSO-ANN model achieves the highest accuracy in terms of the metrics RMSE (0.019), R (0.996), R20.990,MAE (0.013), RMSLE0.013,and MAPE (3.46 %). It performs better than the PSO-ANN model (RMSE 0.026, R 0.975, R20.982,MAE 0.019, RMSLE0.019,and MAPE 5.73 %), and better than the ANN (RMSE 0.046, R0.991, R20.944,MAE 0.034, RMSLE0.032 and MAPE 9.31 %). The RGPSO, PSO and other optimization algorithms are then applied to minimize the surface waviness of a WAAM component. RGPSO achieved the optimal value (0.1631 mm), which corresponds to a 12.6 % reduction compared to the best value obtained using PSO.

Additive manufacturing by the selective paste intrusion: Effect of the distance of the print nozzle to the particle bed on the print quality

Selective Paste Intrusion (SPI) is an additive manufacturing (AM) process in which thin layers of aggregates are selectively bonded by cement paste only where the structure is to be produced. In this way, concrete elements with complex geometries and structures can be created. Reinforcement is required to increase the flexural strength of the concrete elements and, thus, enable their applicability in practice. Integrating the reinforcement is a difficult task, particularly in the case of SPI, due to the layerwise printing method. Especially with respect to possible complex structures, the production of the reinforcement needs to be adapted to SPI, thereby offering a high degree of freedom. One concept for reinforcement integration is combining the two additive manufacturing processes, SPI and Wire and Arc Additive Manufacturing (WAAM). However, since the two processes serve different fields of application, their compatibility is not necessarily given. Ongoing investigations show that the temperatures caused by WAAM adversely affect both the cement paste rheology required for sufficient paste penetration into the particle bed and the overall concrete strength. This paper provides an overview of ongoing research focusing on different cooling strategies and their effects on the compressive strength of SPI-printed concrete parts.

Microstructure and mechanical properties of wire and arc additive manufactured 2319 aluminum alloy treated by laser shock peening

The components manufactured by Wire and Arc Additive Manufacturing (WAAM) have some problems to be solved urgently, such as uneven microstructure, numerous pore defects, and residual tensile stress. Laser Shock Peening (LSP) is an innovative and advanced surface modification technology that improves mechanical characteristics by inducing significant plastic deformation and high compressive residual stress on metal surfaces. Therefore, combining LSP with WAAM is expected to solve its existing problems. In this work, LSP with different energy parameters was used to post-process the WAAM 2319 aluminum alloy. The results indicated that LSP could improve the microstructure, eliminate near-surface pores, harden the surface layer, and induce a residual compressive stress layer, and the effect was more effective with the increase of laser energy applied. The yield strength of the peened specimens significantly increased by 60.73 %, and the ultimate tensile strength also increased by 16.03 %. The hole fatigue life of the peened specimens was significantly improved, increasing by 179.8 % and 261.7 %, respectively, applying laser energies of 5 J and 10 J. Therefore, the engineering industry may benefit from a combination of LSP and WAAM technology.

Effect of combined parametric impacts on collapsing the wall quality of WAAM Al5356 component

Even though Wire and Arc Additive Manufacturing (WAAM) of the Al5356 component has garnered attention for making affordable, large-scale components, problems with porosity, humping, and undercut still exist. Therefore, optimising process parameters is crucial to achieving flawless products with consistent layer deposition. Hence in this research, the most important WAAM parameters including travel speed (TS), wire feed speed (WFS), and torch angle (TA), were examined in order to determine how they affected structural integrity while taking into account key responses such as porosity, pore diameter, and tensile strength. The Significance of Criteria Weighted Aggregated Sum Product Assessment (WASPAS) in conjunction with Intercriteria Correlation (CRITIC) was used to investigate the favourable circumstances and confirm that the TA is the most important parameter in the nucleation of pores. The verification studies demonstrate that a 58.2 % reduction in pore diameter results in a 31.8 % increase in tensile strength. An ideal TS and WFS of 65 cm/min and 5 m/min, with a maximum TA of 90°, were found to be the favorable conditions for printing Al5356 wall with a minimum porosity of 0.037 %, enhanced ultimate tensile strength of 278 MPa, and minimum pore diameter of 93 µm, according to the CRITIC associated WASPAS approach. Additionally, using the fractography, the damage process based on the porosity creation was investigated. The optimal parameters for generating a defect-free multi-layer structure were identified, hence enhancing the structure’s suitability for industrial use.

Full-field measurements of the microstructure’s effect on the mechanical behaviour of a wire and arc additively manufactured duplex stainless steel

Wire and Arc Additive Manufacturing (WAAM) is particularly well suited to the fabrication of large-scale structural components. Its use for the deposition of Duplex Stainless Steel (DSS) structures is especially sought upon by the naval industry. Although additively manufactured materials usually come with heterogeneous microstructure, residual stresses, internal and surface defects that must not jeopardize the structural integrity of components. In this context, the present study aims to analyse the as-deposited microstructure of a WAAM DSS and its influence on the mechanical behaviour via mechanical field measurement using both Digital Image Correlation (DIC) and Thermoelastic Stress Analysis (TSA).

Numerical investigation and design methods of the local buckling of WAAM stainless steel circular hollow section stub columns

3D printing is an advanced technology that has been used in biomedical and automotive engineering, and has raised a significant response in civil engineering. Wire and arc additive manufacturing (WAAM), a metal 3D printing technology, has prospective applications in steel construction because it can fabricate large-scale structural members at an acceptable cost and manufacturing efficiency. Fundamental studies are still urgently needed to realize its engineering application. However, due to the irregular geometric features, limited studies on the structural performance of WAAM components, particularly the numerical studies, have been carried out. To this end, a numerical investigation on the local buckling of WAAM stainless steel circular hollow section (CHS) stub columns under axial compression has been conducted and presented herein. The finite element (FE) models were established and validated against the existing experimental research. Parametric studies were subsequently carried out to broaden the cross-sectional resistance data pool using the developed FE models. The applicability of the cross-section design provisions specified in EN 1993-1-4:2006 + A2:2020, ANSI/AISC 370-21 and the continuous strength method (CSM) for the design of WAAM CHS was evaluated according to the experimental and FE results. Furthermore, a modified design method with improved accuracy was suggested.

Wire arc additive manufacturing method for Ti–6Al–4V alloy to improve the grain refinement efficiency and mechanical properties

Wire and arc additive manufacturing (WAAM) technique has introduced a novel approach for producing complex Ti–6Al–4V parts with metric dimensions. However, the produced part leads to the development of a strong texture and anisotropic mechanical properties due to the formation of large columnar β grains. To resolve this issue, the plastic deformation of each deposited track through hammer peening was developed as a means to refine these large β grains. In this study, we have investigated an innovative approach to further enhance the efficiency of β grain refinement by minimizing the arc heat input associated with previous deposited layer, which is achieved by employing a C-type filler wire. Our findings reveal a notable enhancement in grain refinement efficiency through the utilization of a C-type filler wire with peening process, as compared to available conventional commercial round shape filler wire. Specifically, the employment of the C-type filler wire results in a reduced melt pool penetration depth of WAAM Ti–6Al–4V (3.3 mm), compared to the commercially available round shape (R-Type) filler wire (4.48 mm). Within the plastically deformed region by peening, fine and randomly oriented β grains are observed, extending to a depth of deformation reaching 844 ± 32.65 μm. Peening WAAM Ti–6Al–4V with the C-type filler wire leads to the development of isotropic mechanical properties in both horizontal and vertical directions, offering high strength due to the presence of small equiaxed β grains and thin α laths (0.56 ± 0.18 μm), in contrast to the use of conventional commercial round shape filler wire.

Experimental Studies on the Anisotropic Fatigue Behaviour of IN718 Fabricated via Wire Arc Additive Manufacturing

Wire and arc additive manufacturing (WAAM) offers promise in creating large complex structures due to its flexibility and high material deposition rates. The nickel-based alloy IN718 is favoured for WAAM due to its weldability and compatibility. However, WAAM can introduce issues like anisotropic grain structure, porosity, and residual stresses which can lead to directional variations in tensile, fatigue, and fracture behaviour. This paper studied the WAAM process of IN718, utilising cold metal transfer (CMT). The optimised CMT-WAAM parameters for IN718 were identified to as a wire feed speed of 8–10 m/min and a torch travel speed of 0.5–0.7 m/min, resulting in stable deposition and minimal defects. Nevertheless, columnar grain structures were observed in the build direction (BD), with coarse grains in the wall-length direction (WD). This anisotropic microstructure coupled with stress concentrators, contributes to the directional dependence observed in tensile properties, fatigue endurance, and crack growth. The investigation revealed superior ductility in the BD compared to the WD. Interestingly, the fatigue endurance testing showed a longer life in the WD compared with the BD, attributed to stronger stress concentrators in the BD specimens. However, when examining a cracked specimen, the fatigue crack propagated faster in the WD rather than the BD.

Wire and arc additive manufacturing for strengthening of metallic components

Wire and arc additive manufacturing (WAAM), also known as wire arc directed energy deposition (WA-DED), offers valuable capabilities not only for manufacturing but also for strengthening and repairing aging components. This paper employs the finite element (FE) method to investigate the influence of deposition parameters on the strengthening efficiency of damaged steel plates strengthened by WAAM material. The study calibrates the inherent strain method (ISM) with thermo-mechanical analysis to accurately predict residual stresses (RS) in manufactured samples, demonstrating that the ISM enhances computational efficiency while effectively predicting RS. It thoroughly examines key parameters such as the deposition direction, maximum thickness, and the geometric configuration of the WAAM material, including shapes and in-plane dimensions. The results indicate that deposition perpendicular to the loading direction provides better performance compared to deposition along the loading direction as it induces less normal and through-thickness stresses. Furthermore, this research determines the optimal maximum thickness for the WAAM material, showing that an increase in thickness can lead to higher maximum tensile stresses at the interface between the newly WAAM material and the underlying base plate. The study also establishes the optimal in-plane dimensions for the WAAM material. The results suggest placing the maximum thickness of WAAM material near the damaged area and gradually decreasing it in two directions to ensure sufficient stiffness around the cracked area, while avoiding an abrupt change in stiffness. This approach generates appropriate compressive stresses around the crack tip and decreases maximum tensile stresses in the plate. The study further illustrates that employing a proper printing strategy without a subsequent machining process can effectively reduce the maximum tensile stress in the steel plate while minimizing material usage.

Additive manufacturing of AISI 304L stainless steel: A review of processing parameters and mechanical performance

Additive manufacturing (AM) has become a favorable method for producing 304L stainless steel (SS) for various industrial applications, which is owing to its favorable characteristics including corrosion resistance, mechanical performance, and design flexibility. This review paper presents a comprehensive overview of the processing factors along with the mechanical performance of AM-fabricated 304L SS (AM304LSS). Firstly a discussion is provided for the fundamental principles of AM techniques that are common for processing SS304L. This includes selective laser melting (SLM), laser beam powder bed fusion (LB-PBF), direct metal laser sintering (DMLS), directed energy deposition (DED), wire-and-arc additive manufacturing (WAAM). Subsequently, the impact of key processing factors i.e. laser power, and powder characteristics on the microstructure and mechanical properties of AM304LSS is presented. In addition, this article examines recent progress in process optimization strategies and post-processing techniques for improving and enhancing the mechanical properties and surface finish of AM 304L stainless steel components. Finally, significant insights are provided for researchers, engineers, and practitioners involved in the advancement and application of AM304LSS components.

Isotropy of fatigue crack growth in hybrid additive manufactured Ti6Al4V ELI titanium alloy

In the present paper, the effects of macrostructure and microstructure on fatigue crack growth (FCG) behavior of wire and arc additive manufacturing (WAAM) and hybrid additive manufacturing with in-situ rolling (HAMR) were investigated in three sampling directions for Ti6Al4V ELI. The results demonstrate that WAAMed samples exhibit coarse columnar grains with zigzag boundaries, interlayer heat affected band (HAB), and basketweave microstructures. The fatigue crack growth rate (FCGR) is lowest in the Y-X direction while being similar between the X–Y and X-Z directions, indicating significant anisotropy. This difference can be attributed to changes in plastic region size and internal slip characteristics near the crack tip caused by variations in macrostructure and microstructure. After applying HAMR with quasi-β heat treatment, interlayer HABs are eliminated, resulting in uniform equiaxed grains and colony microstructures. The FCGR curves in three directions significantly overlap without any observed anisotropy, which are lower than those obtained for traditionally forged materials. Therefore, the isotropic FCGR of plastic materials can be reduced by achieving a nearly flawless metallurgical quality and ensuring uniform equiaxed grain matching with the corresponding critical colony size and fine thickness lamellae. The findings suggest that the application of quasi-β heat treatment in conjunction with HAMR offers a promising high-efficiency manufacturing technique for producing isotropic titanium alloy forgings characterized by exceptional damage tolerance.

Microstructural causes and mechanisms of crack growth rate transition and fluctuation of additively manufactured titanium alloy

Wire and arc additive manufacturing (WAAM) enables rapid near-net-shape fabrications of large-size parts and in-situ remanufacturing in many industry sectors. A comprehensive understanding of the fatigue failure mechanism of WAAM titanium alloys is a prerequisite for their widespread use in critical structural components subject to fatigue load. Here, the fatigue crack growth behavior of WAAM TA15 material is investigated. Fatigue crack growth tests are performed using compact tension specimens sampled from different locations and with different crack orientations of the WAAM TA15 block. The fatigue crack growth rate (FCGR) data exhibit two governing rates separated by a transition stress intensity factor value, ΔKn, and the degrees of fluctuation of the FCGR data in the two regimes are notably different. A piecewise log-linear model is first proposed by incorporating the Heaviside step function and ΔKn into the classical Paris’ model, allowing for the transition ΔKn to be determined by the data. The potential causes of the transition ΔKn are phenomenologically inferred via fractography and surface roughness profiling results. The critical microstructure affecting the value of ΔKn is identified by relating the crack tip cyclic plastic zone size at ΔKn to the sizes of main microstructures. The cause of different degrees of fluctuations in the two regimes separated by ΔKn is inferred by examining the microstructures within the plastic zone. The microstructural mechanisms of the local FCGR reduction and fluctuation are further identified and explained.

Correlated high throughput nanoindentation mapping and microstructural characterization of wire and arc additively manufactured 2205 duplex stainless steel

Duplex stainless steels (DSS) in wire and arc additive manufacturing (WAAM) have attracted significant research attention due to their mechanical properties and corrosion resistance. This study uses conventional and nanomechanical testing methods to compare the mechanical and microstructural behaviors at macroscopic and microscopic length scales. Macro hardness (HV10) testing yielded 259 and 249 in low and high heat input (HI) samples, respectively, while ferrite content averaged 52.7 and 48.5%. However, these results fail to provide conclusive insight into the potential influence of microstructural variations at the macroscopic level, likely due to the composite response of the material. To overcome this limitation, the mechanical response of the DSS samples is assessed at the grain level via high throughput nanoindentation mapping with image processing to track the location of each indent. This approach enabled differentiating the indents landing on ferrite and austenite phases as well as those landing on the interfaces. The results showed that the austenite phase had higher hardness (4.30 and 4.35 GPa) than the ferrite phase (3.89 GPa and 4.03 GPa) for high and low HI samples, respectively. The observed differences in hardness between the phases can be attributed to higher nitrogen content in the austenitic phase.

CUTTING TOOL DESIGN FOR MILLING OF THIN-WALLED INCONEL 718 COMPONENTS MADE BY WAAM

The paper deals with the issue of chatter reduction by modification of both the cutting tool geometry and the machining strategy. Tool wear, cutting forces, surface roughness, and flatness of milled thin-walled parts produced by WAAM (Wire and Arc Additive Manufacturing) technology are evaluated. The machining strategy and parameters of the cutting tool macrogeometry were designed on the basis of experimental machining. Due to the combination of custom geometry of the cutting tool and adapted machining strategy, it is possible to significantly reduce chatter during milling and thereby reduce the roughness of the machined surface, as well as improve machining precision. The experimental results contribute to the effort to expand the knowledge in the field of machining thin-walled parts.

Comparison of STP and TP Modes of Wire and Arc Additive Manufacturing of Aluminum–Magnesium Alloys: Forming, Microstructures and Mechanical Properties

Aluminum–magnesium (Al–Mg) alloys, known for their lightweight properties, are extensively utilized and crucial in the advancement of wire and arc additive manufacturing (WAAM) for direct high-quality printing—a focal point in additive manufacturing research. This study employed 1.2 mm ER5356 welding wire as the raw material to fabricate two sets of 30-layer thin-walled structures. These sets were manufactured using two distinct welding modes, speed-twin pulse (STP) and twin pulse (TP). Comparative evaluations of the surface quality, microstructures, and mechanical properties of the two sets of samples indicated that both the STP and TP modes were suitable for the WAAM of Al–Mg alloys. Analyses of grain growth in the melt pools of both sample sets revealed a non-preferential grain orientation, with a mixed arrangement of equiaxed and columnar grains. The STP mode notably achieved a refined surface finish, a reduced grain size, and a slight increase in tensile strength compared to the TP mode. From the comparison of the tensile data at the bottom, middle, and top of the two groups of samples, the additive manufacturing process in the STP mode was more stable.