Wire And Arc Additive Manufacturing Research Articles

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.

Investigating the Forming Characteristics of 316 Stainless Steel Fabricated through Cold Metal Transfer (CMT) Wire and Arc Additive Manufacturing

Wire and arc additive manufacturing (WAAM), recognized for its capability to fabricate large-scale, complex parts, stands out due to its significant deposition rates and cost-effectiveness, positioning it as a forward-looking manufacturing method. In this research, we employed two welding currents to produce samples of 316 austenitic stainless steel utilizing the Cold Metal Transfer wire arc additive manufacturing process (CMT-WAAM). This study initially evaluated the maximum allowable arc travel speed (MAWFS) and the formation characteristics of the deposition bead, considering deposition currents that vary between 100 A and175 A in both CMT and CMT pulse(CMT+P) modes. Thereafter, the effect of the CMT+P mode arc on the microstructure evolution was analyzed using the EBSD technique. The findings indicate that the arc travel speed and deposition current significantly affect the deposition bead’s dimensions. Specifically, an increase in travel speed or a reduction in current results in reduced bead width and height. Moreover, the employment of the CMT+P arc mode led to a reduction in the average grain size in the mid-section of the sample fabricated by CMT arc and wire additive manufacturing, from 13.426 μm to 9.429 μm. Therefore, the components of 316 stainless steel produced through the CMT+P-WAAM method are considered fit for industrial applications.

Hybrid interlayer hot rolling and wire arc additive manufacturing of Al-Mg alloy: Microstructure, mechanical properties and strengthening mechanism

Considering the deformation-strengthening benefits of Al-Mg alloy and the high forming efficiency offered by wire and arc additive manufacturing (WAAM), the microstructure evolution and strengthening mechanism of hybrid interlayer hot rolling and wire arc additive manufacturing (HR-WAAM) samples have been systematically investigated in this study. The results indicate that interlayer hot rolling can effectively reduce the size and number of pores, which diminishes the stress concentration areas. Additionally, rolling deformation significantly enhances the effect of dislocation strengthening. Furthermore, a high density of dislocations can promote recrystallization to refine grain size, while also improving grain orientation, all of which contribute to better stress distribution. Due to these reasons, the strength and toughness of the alloy are notably improved. The average ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) values achieved by HR-WAAM samples were 338 MPa, 276 MPa, and 20.9%, respectively. These values represent increases of 28.5%, 41.5%, and 38.4% compared to conventional WAAM samples. These findings are expected to provide an efficient and cost-effective method for additive manufacturing (AM) of deformation-strengthened aluminum alloys.

Hot deformation behavior and process optimization of TC4-DT alloy fabricated by wire and arc additive manufacturing with in-situ forging

The near net shape forging of a preform fabricated using additive manufacturing (AM) technique has attracted significant attention due to its exceptional material utilization rate. However, the complexity of the parts hinders its further development. This study investigated the hot deformation behavior of TC4-DT titanium alloy fabricated by wire and arc additive manufacturing (WAAM) with in-situ forging. The isothermal compression samples underwent homogenizing treatment to eliminate layer bright lines before being subjected to deformation at temperatures ranging from 800 to 950 °C and strain rates ranging from 0.01 to 1 s−1 with the height reduction of 60%. Subsequently, the hot deformation constitutive equations and hot processing map were established to analyze the characteristics of hot deformation and microstructure evolution. The results demonstrate that the hyperbolic sine constitutive equation considering strain can accurately predict flow stress under arbitrary deformation conditions, with an average relative error of 7.23%. Furthermore, microstructure analysis under different deformation conditions validated the applicability of the hot processing map, which identified preferable and easily achievable in-situ hot forging regions at temperatures between 900 and 950 °C and strain rates between 0.05 and 1 s−1 with the strain exceeded 0.4. Finally, WAAM combined with optimized in-situ hot deformation processing enables the production of macrostructures consisting of fully equiaxed prior-β grains while maintaining isotropy in mechanical properties, thereby providing a solid foundation for direct additive manufactured complex forgings featuring uniformly fine equiaxed grains and highly comprehensive properties.

Influence of different deposition strategies on the microstructure and mechanical properties of the laminated heterostructured material with ER130S-G HSS and 316 L SS fabricated by WAAM

Two groups of laminated heterostructured materials (LHM) thin walls with different deposition strategies and the corresponding single-material thin walls were successfully fabricated by wire and arc additive manufacturing (WAAM) technology. The deposition strategy for the LHM-1 thin walls was to change the deposited material every layer, and for the LHM-2 thin walls was to change the deposited material every two layers. The results indicate that changes in the deposition strategy could affect the volume fractions and distribution locations of different phases in LHM samples, thereby influencing the mechanical properties. Due to the dilution effect, when the two materials in the LHM samples were deposited on each other, the chemical composition of the two regions deviated. Two sets of LHM samples were prepared using the same volume fraction of 316 L stainless steel (SS) and ER130S-G high-strength steel (HSS), and the LHM-1 samples showed higher tensile strength and lower elongation. In HSS areas of the LHM-1 sample, every layer consisted of the martensite microstructure. In the HSS areas of the LHM-2 sample, one layer was composed of the martensite microstructure, while the adjacent layer was a mixed microstructure of bainite and ferrite. For LHM samples, the softer regions experiencing greater deformation during the tensile process. The lower Schmid factor of the FCC phase in the LHM-2 sample compared to the LHM-1 sample, makes it easier for the former to yield, thereby resulting in superior ductility of the LHM-2 sample. The results of the investigate reveal that the possibility of controlling the microstructure and properties by altering deposition strategies in WAAM technology.

Mathematical analysis and process optimization of wire and arc additive manufactured Ti6Al4V ELI alloy with in-situ rolling

The combination of wire and arc additive manufacturing (WAAM) and rolling offer the advantages of high efficiency, low cost, and fine grain, making it a viable option for the rapid production of aerospace thin-wall forgings using titanium alloy. However, the interplay between various factors such as temperature gradient, deformation force, and prior pass morphology directly influence the morphology and grain evolution before and after subsequent pass deformations, which lead to insufficient overall morphological accuracy and grain refinement uniformity. Building upon theoretical analysis, numerical simulation, and experimental verification, this study focuses on investigating the metal flow behavior and grain evolution mechanism during WAAM with in-situ rolling single-pass multi-layers. By establishing correlations between morphology, microstructure, temperature, stress-strain and deformation characteristics, the process optimization strategies of large width-height ratio, shallow melting depth and fixed width spread were proposed. These findings can provide theoretical support for the deformation machine design and the high-precision, uniformly fine grains additive manufacturing of thin-walled titanium alloy forgings.

Investigation on the elastic flexural stiffness of dot-by-dot wire-and-arc additively manufactured stainless steel bars

Among different metal additive manufacturing (AM) technologies, arc-based Directed Energy Deposition, also known as Wire-and-Arc Additive Manufacturing (WAAM), is considered the most suitable for large-scale structural components production. In particular, the WAAM printing strategy referred to as “dot-by-dot” allows the realization of complex 3D lattice forms at the scale of structural steel parts, composed of unitary cells made of slender bars. Nonetheless, the outcomes of this process are still to be properly investigated in terms of their mechanical behavior under various loading conditions. To assess the buckling behavior of WAAM-produced slender bars, extensive effort is requested to properly characterize the main driving aspects, namely the flexural stiffness possibly influenced by mechanical anisotropy induced by the printing process and the influence of the geometrical imperfections. The present work reports the first results of experimental bending tests conducted on vertically printed (i.e. with a fixed build angle equal to 0°) straight dot-by-dot WAAM stainless steel bars, as an initial investigation towards a more comprehensive analysis of the buckling behavior of WAAM slender elements. The results are then interpreted by introducing three approaches of increasing complexity, including two analytical approaches based on a simplified idealization of the real geometry of the bar, and a third approach based on the reconstruction of the real geometry of the bar using advanced numerical simulations and 3D scanning. The three approaches lead to a different appraisal of the influence of the geometrical irregularities on the flexural stiffness of the specimens. The main results of the present study could be utilized to interpret the results of future experimental compressive tests on WAAM slender elements and to develop ad-hoc buckling curves for structural design purposes.

Mechanical Anisotropy and Failure Analysis of Inconel 625 Parts Manufactured Using Wire and Arc Additive Manufacturing (WAAM)

Mechanical Anisotropy and Failure Analysis of Inconel 625 Parts Manufactured Using Wire and Arc Additive Manufacturing (WAAM)

Investigation of the thermal gradients formed during the process of cooling of WAAM built Al99.7 specimen

This work presents a preliminary experiment used to determine the possibility of developing a thermal model used to predict the thermal gradients formed during the process of wire and arc additive manufacturing (WAAM). For this purpose, an Al99.7 specimen was built using gas metal arc welding (GMAW) in the cold arc pulse mode. The temperature of both the substrate and each consecutive layer was measured using thermocouples and infrared thermometers and the experimental data was used for the calibration of the developed thermal model. The obtained results can be used for the further development of the thermal model.

Effect of welding mode on selected properties of additively manufactured AA5087 aluminium alloy parts

Wire and arc additive manufacturing (WAAM) is a popular direct energy deposition (DED) method for producing large-scale metallic components. The main advantages of the technique are a high deposition rate and low cost. Furthermore, the utilization of the WAAM is prevalent in the aerospace industry. The AA5087 aluminium alloy with 4.5 wt.% of magnesium has been investigated because of its excellent properties. The present research deals with the study of thermal cycles and fields developed in the alloy during additive manufacturing with two different Cold metal transfer (CMT) modes, namely conventional (CMT) and cycle-step (CMT-CS). The welding system was equipped with a Fronius TransPulse Synergic 3200 CMT power source, a Fanuc Arc Mate 1000iC 6-axes robot with an R 30iA control unit, a welding torch, and a 1-axis positioner. The AA5087 aluminium alloy welding wire with a diameter of 1.2 mm was deposited onto the AA5083 aluminium alloy plate with dimensions of 70 mm x 200 mm x 3 mm during the experiment. The thermal cycles were documented using an Ahlborn Almemo 5690-2 measuring station equipped with K-type thermocouples. The thermal fields were monitored with a FLIR E95 thermography camera. The results showed the evident influence of arc mode on the temperatures developed in manufactured aluminium alloy parts during the process of WAAM.

Phase-field modeling and Experimental investigation for rapid solidification in wire and arc additive manufacturing

The rapid solidification speed and significant temperature gradient observed in the wire and arc additive manufacturing (WAAM) process result in a deviation of the solid-liquid interface from the equilibrium state assumed by the conventional directional solidification phase field (PF) model. This, in turn, limits the ability of the traditional directional solidification PF model to accurately depict the microstructure evolution in additive manufacturing, where non-equilibrium effects dominate. In this work, we employed a 3D finite element (FE) model to simulate the temperature distribution during the wire and arc additive manufacturing (WAAM) process. Additionally, a modified PF model that applies to additive manufacturing is also used to simulate the dendrite morphology and solute segregation behavior in the WAAM process at different scanning speeds. Experimental validation of the simulation results was also conducted. We observed a significant reduction in dendrite growth velocity and solute segregation with increasing scanning speed, attributable to the combined effects of the temperature gradient G(t) and solidification speed Vp. Furthermore, higher scanning speeds were found to increase the primary dendrite arm spacing (PDAS) and average dendrite width. Importantly, our results demonstrated a quantitative agreement between the simulation results using the modified directional solidification PF model and the experimental observations. This approach provides a foundation for selecting and predicting processing parameters and microstructural characteristics under additive manufacturing conditions, facilitating a comprehensive analysis of dendrite growth and solute segregation at different scanning speeds in the WAAM process.

Analysis of Machinability on Properties of Inconel 718 Wire and Arc Additive Manufacturing Products

Wire and arc additive manufacturing (WAAM) is a metal deposition technique with a fast rate and the possibility of a high volume of deposition. Because of its fast deposition and high heat input, the manufactured products have poor surface quality. This paper presents a study on the machining of Inconel 718 wall-shaped additive manufacturing (AM) products, a necessary step for the improvement of surface quality. Considering the possibility that the characteristics of the milling processes of AM products might differ from those of traditionally manufactured parts, in this research, two types of Inconel 718 were studied and compared: one was manufactured using WAAM, and the other was an Inconel 718 rolled bar (Aerospace Material Specifications 5662). Using the testing procedure, a conventional two-flute cutting tool was used to assess their machinability. For this process, multiple passes were performed at three different heights of the samples. Considering the peculiarities of the AM products, such as their uneven surfaces, dendritic microstructures, and anisotropy, the results were analyzed. After the machining operation, the effects on the products were also studied by analyzing their surface quality. This study found a higher stability in the cutting process for the AMS 5662 samples relative to the WAAM parts with less variability in the cutting forces overall, resulting in better surface quality.

Detection and quantitative evaluation of surface defects in wire and arc additive manufacturing based on 3D point cloud

ABSTRACT Wire and Arc Additive Manufacturing (WAAM) with high efficiency and low-cost is an economical choice for the rapid fabrication of medium-to-large-sized metallic components and has attracted great attention from scholars and entrepreneurs in recent years. However, defects such as porosity, and humps, could occur occasionally after each layer of deposition on weld bead surfaces due to disturbances and process abnormities. Detection and quantitative evaluation of weld bead defects is crucial to ensure successful deposition and the quality of the entire component. In this paper, a novel defect detection and evaluation system was developed for WAAM utilizing machine vision technology. The system incorporated new defect detection algorithms based on analysing the 2D curvature of the weld bead height curve and the 3D curvature of the weld bead point cloud. Furthermore, a defect evaluation algorithm was developed based on reconstructing the normal weld bead contour using geometric features extracted from the accumulated point cloud. This system enables the automatic detection of weld bead morphology during the WAAM process, offering important information about the location, type, and volume of defects for effective interlayer repairs and enhanced part quality.

Manufacturing of a demonstrator using WAAM technology on the Addilan V0.1 machine.

Manufacture of a medium-sized demonstrator of the aerospace industry based on WAAM, identifying the key aspects to be considered in the manufacture of this type of parts. One of the project lines of TKNIKA's area of specialization in Additive Metal Manufacturing is related to the WAAM (''Wire and Arc Additive Manufacturing'') technology. This process is classified into the Directed Energy Deposition (DED) family process and as his description says is based on the deposition of a wire melted under the action of an electric arc . The main objective is the generation of knowledge through practice and experimentation in a network between different VET teachers and schools. A medium-sized part has been selected, with a simple geometry, which would normally be manufactured from a metal block or a forged preform. In this case, an arc-wire manufacturing process can be a very interesting alternative. The main objective of this practice is to produce a quality preform, identifying the key aspects that allow it to be manufactured, in a controlled manner, on the Addilan WAAM V0.1 manufacturing machine. The solution has been consisted on manufacturing three-piece series based on previous experiences. Image 3: Result as Machined VS as WAAMed

Blended structural optimization of steel joints for Wire-and-Arc Additive Manufacturing

Metal Additive Manufacturing, and in particular Wire-and-Arc Additive Manufacturing (WAAM) has proved to be a great and efficient alternative to the common subtractive manufacturing processes to realize complex-shape members and connections for construction. With reference to complex spatial structures such as gridshells, the connections play a crucial role both in the design and the construction processes. Novel computational design tools allow designers to conceive optimized joint solutions while minimizing the material use, resulting in difficult geometries to be fabricated with conventional methods. The present work aims at providing an innovative integrated design and fabrication framework to efficiently apply topology optimization algorithms to improve the efficiency of steel joints in complex spatial structures. The framework is based on the so-called “blended” structural optimization approach aimed at incorporating manufacturing constraints, basic principles of conceptual structural design and structural requirements into topology optimization to design ready-to-fabricate complex steel joints. The designs are suitable for fabrication with the WAAM process. The approach is applied to a case study to re-design the joint connections of the world’s renowned British Museum gridshell rooftop structure. From a catalogue of various designs for each unique joint, one selected design is optimized and then checked for structural requirements in terms of strengths and stiffness. Then the optimized joint is validated for fabrication with WAAM process.

Maximising the Deposition Rate of 5356 Aluminium Alloy by CMT-Twin-Based WAAM While Reducing Segregation-Related Problems by Local IR Thermography

The CMT-Twin-based wire and arc additive manufacturing (WAAM) process for 5356 aluminium alloy has been investigated focusing on the optimisation of welding parameters to maximise the deposition rate while avoiding segregation-related problems during solidification. For that, different conditions have been studied regarding interpass dwell time and the use of forced cooling. The larger heat input produced by the double-wire CMT-Twin process, compared to the single-wire CMT, creates vast segregations for less intensive cooling conditions and short dwell times that can induce cracks and reduce ductility. Thermography has been applied to set a maximum local temperature between consecutive layers avoiding those segregations and pores, and to optimise the total manufacturing time by varying the interpass dwell time along the height of the wall. Only a constant interpass long dwell time of 240 s and the new optimised strategy were effective in avoiding merged segregations, reducing the latest total manufacturing time by 36%. Obtained tensile properties are comparable to other works using WAAM for this alloy, showing lower properties in the vertical orientation. The use of CMT-Twin-based welding technology together with variable interpass dwell time controlled by thermography is an interesting alternative to build up parts with wall thicknesses around of 10 mm in a reduced time.

Interpass temperature effects on WAAM ER316L stainless steel corrosion using potentiostatic pulse tests

The effect of interpass temperature on the microstructure and pit nucleation behaviour in wire and arc additive manufacturing (WAAM) deposited ER316L stainless steel is investigated. Lowering the interpass temperature increases the ferrite content and decreases the sigma phase precipitation. Potentiostatic pulse measurements show that the WAAM ER316L pits develop predominantly near sigma phases and have higher pit density compared to a wrought 316L (UNS S31600). The pitting susceptibility of WAAM ER316L increases with increasing interpass temperature due to the precipitation of larger sigma phase enhancing the elemental segregation.

Enhancing Mechanical Properties: Exploring the Effect of Annealing Temperature on Wire Arc Additively Manufactured High-Strength Steel.

This study investigates the mechanical properties of exceptionally high-strength steel produced by wire and arc additive manufacturing (WAAM), using the 304 stainless steel wire and the low carbon wire (LCS). The study found that annealing treatment can enhance the steel's mechanical properties. The microstructure in the LCS layer changed from ferrite to bainite and then to a mixture of austenite, pearlite, and bainite with increasing annealing temperature. In contrast, the SS layer retained its martensitic structure, albeit with altered lath sizes. The annealing treatment also improved the orientation of the grains in the steel. The optimal annealing temperature observed for the steel was 900 ℃, which resulted in a maximum tensile strength of 1176 MPa along the Y direction and 1255 MPa along the Z direction. Despite the superior mechanical properties, the LCS layer still exhibited failure during tensile testing due to its lower hardness. The study suggests that annealing treatment can be a useful technique for enhancing the mechanical properties of high-strength steel in WAAM applications.

Contribution made by double-sized TiC particles addition to the ductility–strength synergy in wire and arc additively manufactured Al–Cu alloys

An Al–Cu matrix composite reinforced with uniformly-distributed micron- and nano-double-sized TiC particles (MNDS-TiCps) was successfully fabricated using a wire and arc additive manufacturing (WAAM) process. The combined effect of the MNDS-TiCps on the precipitation of the θ″ phase, the structural evolution of the grain boundaries, and solidification dynamics of the deposited Al–Cu matrix composites were subsequently investigated. The micron-sized TiC particles in the molten pool generate nucleation undercooling (ΔTnu, ∼0.32 K) which inhibits grain boundary segregation due to constitutional undercooling and promotes the redistribution of the Cu solute in the Al matrix. The phase composition at the grain boundaries changes from θ-Al2Cu to α-Al + θ-Al2Cu and the non-coherent interface between the α+θ transition zone and θ grain boundary is transformed into a coherent interface between the α+θ grain boundary and Al matrix, i.e. (211)θ-Al2Cu//(111)Al. The decrease in free energy within the Al matrix provides energy to facilitate the growth of nuclei on the surface of the nano-sized particles. A semi-coherent interface is thus detected between the TiC and precipitates, characterized by a crystal orientation relationship of (200)TiC//(310)θ″-Al2Cu. The dislocations that provide pipe-diffusion paths for solute Cu constitute a driving force that coarsens the precipitates, promoting the precipitation of θ″ precipitates. Multi-site co-deformation combined with dislocation increment inhibits stress damage to the micro-interface. The strength and elongation increase by 51.0 % and 118 %, respectively, compared to specimens without TiC. This work provides a novel perspective for tailoring WAAM-deposited Al–Cu alloys by achieving favorable structural evolution in the grain boundaries, inducing the precipitation of precipitates, and yielding outstanding synergy between ductility and strength.

Effect of in-situ rolling and heat treatment on microstructure, mechanical and corrosion properties of wire-arc additively manufactured 316L stainless steel

Post-heat treatment and in-situ rolling, both can be used to improve the coarse grains and anisotropy that are prevalent in metallic materials, fabricated by wire and arc additive manufacturing (WAAM). In this study, the effect of in-situ rolling and heat treatment on the microstructure, mechanical and corrosion behaviors of WAAM 316L was investigated. The results showed that the microstructure of WAAM 316L changed considerably due to the introduction of rolling deformation, as it was observed that the ferrite was distributed in a reticulated or equiaxed morphology instead of dendritic distribution, columnar grains were found to be engulfed, while a large number of low angle grain boundaries (LAGBs) with high dislocation density were introduced. After heat treatment at 650 °C, there was no significant change in grain morphology, ferrite gradually transformed into σ phase, the tensile strength increased, yield strength and elongation decreased. After heat treatment above 1000 °C, the strength and ductility of the rolled WAAM 316L were higher than those of the unrolled WAAM 316L. As the heat treatment temperature increased, the corrosion resistance first decreased and then increased. In-situ rolling resulted in a decrease in the corrosion current density of the steel and also reduced the stability of the passive film.