Welding-based Additive Manufacturing Research Articles

Welding-based additive manufacturing processes for fabrication of metallic parts

Additive Manufacturing (AM) is modernizing the manufacturing industry by enabling the layer-by-layer deposition process to manufacture objects in nearly any form with minimum material waste. However, components developed utilizing the AM process have dimensional constraints. To address this issue, AM-produced metal materials can be coupled with various welding processes. This article focuses on the foundations, highlighting the distinguishing features, capabilities, and challenges of welding-based AM processes by categorizing them into two major groups; arc welding-based AM like Cold Metal Transfer (CMT), Gas Metal Arc Welding (GMAW), Gas Tungsten Arc Welding (GTAW), Plasma Arc Welding (PAW), and high-energy density welding based AM like Laser Beam Welding (LBW) and Electron Beam Welding (EBW). The prior study findings of welding-based AM metal components on mechanical characteristics and microstructural characterization have been addressed. This work will aid researchers, academicians, and professional welders since it gathers vital information on welding-based AM processes. Furthermore, current research in the arena of welding-based AM and its future opportunities has been discussed.

WITHDRAWN: Enhancing industrial applicability of aluminum alloys chips recycling through Friction Stir Extrusion: Thin wires production process

Friction Stir Extrusion is one of the most promising solid-state chip recycling techniques because of its relative simplicity and high efficiency. One of the most straightforward applications for the process is the production of recycled wires to be used as filler material in welding or welding-based additive manufacturing processes, in order to create an industrial symbiosis link, fostering a circular economy and enhancing the Technology Readiness Level (TRL) of the process. The scalability of the process to the thin wires needed for such applications has not been investigated so far. In this paper, an experimental and numerical analysis was developed. A dedicated numerical model was first validated and then used to design the tool geometry. The effect of tool rotation and tool force on both “standard” mechanical properties, as UTS and microhardness, and specific properties for the envisaged application, as the wrapping around reels with different radii, was investigated. The numerical model results were used to explain the influence of the process parameters on the distribution of the main field variables, i.e., temperature, strain, and strain rate, as well as on material flow. It was found that a conical shoulder surface favors the conditions for effective solid bonding. Low values of the extrusion force have detrimental effects on the wires properties as they result either in insufficient strain, or hot cracking defects.

Effect of electrode materials and process parameters on deposition characteristics during GMAW-AM

ABSTRACT This experimental investigation introduced the gas metal arc welding-based additive manufacturing to deposit single-layered beads of ER70S–6 and 316 L stainless steel (SS). Different experimental conditions are generated through response surface methodology for illustrating the effect of wire electrode material and deposition parameters on bead characteristics. From parametric analysis, wire feed speed and torch speed are found to be the most controlling factors for bead width, height, deposition area, penetration depth, dilution, and contact angle. Deposition with 316 L SS wire exhibits minimal bead characteristic features than ER70S–6 because of high electrical resistivity that restricts excessive flow of arc current (low thermal energy development) and maintains the molten pool stability. Microstructural transformation from the continuous nature of δ-ferrite into an isolated core-like structure indicates the heat input’s role over grain refinement. X-ray diffraction depicts α-Fe and ϒ-austenite phases (with δ-Fe) in ER70S–6 and 316 L SS deposits.

Toward a sustainable laser powder bed fusion of Ti 6Al 4 V: Powder reuse and its effects on material properties during a single batch regime

Titanium alloy Ti6Al4V is the most used titanium alloy due to its high specific strength, ductility, corrosion resistance, and weldability. Currently, this alloy is produced with a density above 99% with laser welding-based additive manufacturing processes. However, the costs of titanium powder are high, and for critical components, the excess powder is usually not reused. In this work, we characterized the powder and additively manufactured Ti6Al4V parts by reusing the powder of a single batch to determine the impact on morphology, chemical composition, melt pool viscosity, density, microstructure, and tensile and impact strength. We aimed to determine the limits of powder reuse to increase sustainability and reduce the carbon footprint of Laser Powder Bed Fusion (L-PBF). We found that the powders pick up oxygen after each cycle to form an oxide layer up to 20 nm, causing a change in the optical and thermal properties of the titanium powders. This change affected the laser absorption and, with this, the melt pool properties. The powders reused after 18 cycles were responsible for a drop in the relative density of 0.1%. However, the tensile properties remained unchanged. The reused powders also presented a small shift in particle size distribution that did not affect the sphericity and increased flowability. In this work, we proved that the powders of Ti6Al4V alloys could be reused up to 18 cycles without any modification to the tensile properties but with a decrement in the impact strength of 30% for vertical- and 12% for horizontal stress-relieved specimens and 19% and 16% for furnace-annealed specimens, respectively.

Effect of Process Parameters on Arc Shape, Macroscopic Features, and Microhardness in Pulsed GMA–Additive Manufacturing

Gas metal arc welding-based additive manufacturing (GMA–AM) is a promising, low-cost approach to fabricate large-scale and complex geometry components using layer-by-layer deposition of metals. However, the low forming accuracy of GMA–AM still limits its one-off industrial application due to the strong and nonlinear interactions between arc–droplet transfer and molten pool. To fully understand the influential mechanism of this inherent interaction in the GMA–AM process to precisely control the part accuracy, the arc–droplet transfer behavior in the GMA–AM process with different current waveforms was firstly studied experimentally. The phenomena of the arc swing and the differing droplet transfer with the increase in deposited height were interpreted. The thermal force status of the molten pool and its balance boundary conditions were also theoretically analyzed. Finally, the microstructure and the hardness of the AM parts with different cooling times were tested and analyzed. The experimental results demonstrate that using the spray droplet transfer mode can generate a stable AM process under direct current application conditions, but it easily ends the AM process at the third or fourth layer deposition owing to excessive heat input. A more highly accurate deposition morphology can be obtained in one droplet per pulse mode under pulsed current application conditions, which also indicates that the AM process with a constant current welding supply is stabler and easily produces better deposition than the process with a constant voltage welding supply. With the increase in cooling time, the microstructure evolved from fine ferrite to equiaxed ferrite and to columnar ferrite combined with acicular ferrite with a lower proportion of pearlite in the vertical direction of the part, and the average hardness changed to ~168 HV (bottom), ~175 HV (middle), and ~250 HV (top). The analysis indicates that the heat accumulation of the molten pool is a critical factor that affects the deposition accuracy. To this end, a novel strategy that uses the heat accumulation to compensate for the energy formed in the molten pool is proposed to further reduce the arc heat input and weaken the heat accumulation, and its feasibility is discussed.

Effect of welding processes on mechanical and metallurgical characteristics of carbon steel cylindrical components made by wire arc additive manufacturing (WAAM) technique

In recent decades, Additive Manufacturing (AM) has become a viable alternative to the manufacture of metal parts. Wire arc additive manufacturing (WAAM), a welding-based AM technique is an important research area since it permits the economical manufacture of large-scale parts with relatively high deposition rates. This article compares the effect of heat input on mechanical properties of carbon steel cylindrical components fabricated by Gas Metal Arc Welding (GMAW) and Cold Metal Transferred Arc Welding (CMTAW) processes. Firstly, the influence of heat input on the grain size was analysed. Subsequently, the effect of heat input on the tensile properties, impact toughness and hardness of the cylindrical components were studied along the building direction. The cylindrical component made by CMTAW process showed superior tensile properties and higher impact toughness than GMAW component. Similarly, CMTAW component exhibited higher hardness than GMAW cylindrical component. The variations in mechanical properties are mainly due to the appreciable variations that have occurred in the microstructural features and different grain sizes evolved at different heat input levels. The bottom and top regions of the fractured tensile and impact specimens of the components are characterised by dimple structures revealing the ductile fracture.

Development of a deposition framework for implementation of a region-based adaptive slicing strategy in arc-based metal additive manufacturing

PurposeThis study aims to develop and demonstrate a deposition framework for the implementation of a region-based adaptive slicing strategy for the Tungsten Inert Gas (TIG) welding-based additive manufacturing system. The present study demonstrates a deposition framework for implementing a novel region-based adaptive slicing strategy termed as Fast Interior and Accurate Exterior with Constant Layer Height (FIAECLH).Design/methodology/approachThe mentioned framework has been developed by performing experiments using the design of experiments and analyzing the experimental data. Analysis results have been used to obtain the mathematical function to integrate customization in the process. The paper, in the end, demonstrates the FIAECLH framework for implementing region-based adaptive slicing strategy on the hardware level.FindingsThe study showcase a new way of implementing the region-based adaptive slicing strategy to arc-based metal additive manufacturing. The study articulating a new strategy for its implementation in all types of wire and arc additive manufacturing processes.Originality/valueWire-arc-based technology has the potential to deliver cost-effective solutions for metal additive manufacturing. The research on arc welding-based processes is being carried out in different dimensions. To deposit parts with complex geometry and better dimensional accuracy implementation of a novel region-based adaptive slicing strategy for the arc-based additive manufacturing process is an essential task. The successful implementation of an adaptive slicing strategy would ease the fabrication of complex geometry in less time. This paper accomplishes this need of implementing a region-based adaptive slicing strategy as no experimental investigation has been reported for the TIG-based additive manufacturing process.

Effect of Arc Polarity on the Quality of Deposition in GTAW Welding-Based Additive Manufacturing Process: A Preliminary Study

A Gas tungsten arc welding (GTAW)-based additive manufacturing has a potential for manufacturing metallic parts with better dimensional accuracy and dense structure. This paper discusses the issues in the GTAW-based metal deposition process for the positive and negative polarity of the welding electrode in the direct current circuit. The effect of direct current electrode positive (DCEP) and direct current electrode negative (DCEN) polarity on GTAW-based metal deposition process has been discussed. The experimental study has been done with a constant voltage source of ESAB Caddy 2200i welding machine and the metal beads were deposited on the substrate plate of mild steel. The results of these experiments showed that the metal deposited using DCEN polarity has a better dimensional accuracy over DCEP polarity due to its stability in arc formation and proper transmission of heat. The experimental investigation showed that the DCEP polarity causes the deterioration of the tungsten electrode after a few trials. The work done in this paper will help to distinguish between the use of DCEP polarity and DCEN polarity in GTAW-based additive manufacturing process for depositing the metal with better dimensional accuracy and better surface finish.

Improvement in corrosion resistance of wire arc additive manufactured Inconel 625 alloy through heat treatment

In this study, an Inconel 625 component was fabricated by gas tungsten arc welding-based additive manufacturing and the as-deposited specimens were heat treated at 980 and 1100 °C for 1.0 h, respectively. The effects of heat treatment on the corrosion resistance and microstructure were investigated. Potentiodynamic polarization tests showed that the as-deposited Inconel 625 alloy had disparities in corrosion resistance compared with wrought Inconel 625 alloy. The corrosion resistance deteriorated after heat treatment at 980 °C due to needle-like δ phases provided more sites to pitting initiation. While the corrosion potential (Ecorr) increased by 32%, passivation current density (Icorr) decreased by 52% after heat treatment at 1100 °C, which was comparable with that of wrought Inconel 625 alloy. Detailed microstructural examination demonstrated the recrystallization occurred with the dissolution of Laves and δ phases, weakening of 〈001〉 orientation, decrease of low angle grain boundaries and formation of large numbers of stable twin grain boundaries. All the evolution of the crystal and microstructure contributed to the striking corrosion resistance of the 1100 °C heat-treated Inconel 625 alloy.

Advanced computational modelling of metallic wire-arc additive manufacturing

Wire-arc welding-based additive manufacturing (WAAM) is a 3D printing technology for production of near-net-shape parts with complex geometry. This printing technology enables to build up a required shape layer by layer with a deposition of a consumable welding wire, where the welding arc is a source of heat. Welding is usually performed by CNC-controlled robotic manipulator, which provides a controlled location of material layer adding. Because the process itself involves thermo-mechanically complex phenomena, Finite Element-based virtual models are commonly employed to optimize the process parameters. This paper presents advanced computational modelling of the WAAM of a tube. A thermo-mechanical numerical model of the process is calibrated against experimental data, measured as temperature variation at the acquisition point. The virtual modelling starts with a preparation of the tube geometry in CAD software, where the geometry of the single-layer cross-section is assumed. The geometry is then exported to a G-code format data file and used to control robotic manipulator motion. On the other side, the code serves as an input to in-house developed code for automatic FEs activation in the simulation of the material layer-adding process. The time of activation of the finite elements (FEs) is directly related to the material deposition rate. The activation of the FEs is followed by a heat source, modeled with a double ellipsoidal power density distribution. The thermo-mechanical problem was solved as uncoupled to speed-up computation.

Thermal field prediction for welding paths in multi-layer gas metal arc welding-based additive manufacturing: A machine learning approach

Gas metal arc welding (GMAW)-based additive manufacturing (AM) is a key metal 3D printing technology for the fabrication of near-net shape parts. The thermal history of the multi-layer GMAW-based AM process has a significant influence on part quality and substrate deformations, but it is computationally expensive to accurately calculate it based on numerical method or analytical method. Existing data-driven approaches for the thermal field prediction of AM processes show great advantages in efficiency, but they are mainly applied to single-layer parts or the multi-layer parts with fixed geometry. The main contribution of this work is to realize the thermal field prediction of the multi-layer GMAW-based AM processes with arbitrary geometries by a machine learning approach. Firstly, a novel method for the discretization of deposition process was proposed to make the numerical simulation method for the thermal analysis of AM processes more adaptive and flexible. Then, a unique data structure was developed to extract the deposition state data from the results of the numerical simulation method, which generate the data for the training of the proposed machine learning model. Finally, a physics-based machine learning method based on an ensemble learning model was designed to identify the correlation between the deposition stage and its corresponding thermal field. Validation results showed that the prediction accuracy of the developed method exceeded 94 % when compared with the results of the numerical simulation method, while the time cost of a single prediction process was only at the millisecond level.

Mechanical properties of wire arc additive manufactured carbon steel cylindrical component made by gas metal arc welding process

Abstract Wire arc additive manufacturing (WAAM), a welding-based additive manufacturing (AM) method, is a hot topic of research since it allows for the cost-effective fabrication of large-scale metal components at relatively high deposition rates. In the present study, the cylindrical component of low carbon steel (ER70S-6) was built by WAAM technique, using a GMAW torch that was translated by an automated three-axis motion system using a rotation table. The mechanical properties of the component were evaluated by extracting tensile, impact toughness and hardness specimens from the two regions of the building up (vertical) direction. It is found that the tensile properties of the built material exhibited anisotropic characteristics. The yield strength and ultimate tensile strength varied from 333 to 350 MPa and from 429 to 446 MPa, respectively, (less than 5 % variation).

Current mode effects on weld bead geometry and heat affected zone in pulsed wire arc additive manufacturing of Ti-6-4 and Inconel 718

For the last decade, additive manufacturing (AM) has been revolutionising the aerospace industry, building and repairing various components for aircrafts and outer space vehicles. Despite the fact that AM is gaining rapid adoption by the industry, it is still considered a developing technology, with ongoing research in a variety of fields. Wire arc additive manufacturing (WAAM), a welding-based AM technology, is an active field of research as well, because it enables economical production of large-scale metal components with relatively high deposition rates. In this article, the effects on the weld-bead geometry and heat affected zone from high and low frequency pulsed current are explored on Gas Tungsten Arc Welding (GTAW). The materials used in this investigation were selected to be Ti-6-4 and Inconel 718, both highly used in the aerospace industry for their high strength-to-weight ratio and strength at elevated temperatures respectively. The design of the experiments followed a Taguchi-inspired orthogonal array, altering, apart from the current modes and values, the torch travel speed driven by an industrial robotic arm as well as the wire-feeding rate. The results demonstrate the ability to control both the weld-bead dimensions and penetration depth, as well as the heat affected regions, by utilizing the dual pulsing combination of both high and low frequency pulsing. Alterations from wide beads with deep penetration to narrower beads with greater height-to-width ratios are demonstrated in a single manufacturing setup, enabling further development of the WAAM process.

Microstructural and mechanical characteristics of 308L stainless steel manufactured by gas metal arc welding-based additive manufacturing

In this paper, gas metal arc welding-based additive manufacturing (GMAW-AM) was used to build thin-walled 308L stainless steel parts. The microstructural and mechanical characteristics of the built thin walls were investigated. The results show that the GMAW-AM thin-walled 308L is dominantly composed of columnar dendrites, which grow along the build direction when increasing the number of depositing layers. The microstructure of the GMAW-AM thin-walled 308L mainly consists of two phases: a small amount of δ ferrite phases displayed within γ austenite dendrites. The microhardness of built materials ranges from 155 ± 1.20 HV0.1 to 169 ± 5.67 HV0.1. The average ultimate tensile strength (UTS), yield strength (YS) and elongation (EL) of the GMAW-AM thin-walled 308L in the vertical direction are 531.78 ± 4.52 MPa, 343.67 ± 7.53 MPa, and 39.58 ± 1.38%, respectively, which are obviously lower than those in the horizontal direction (UTS: 552.95 ± 4.96 MPa, YS: 352.69 ± 8.12 MPa, and EL: 54.13 ± 1.29%).

A preliminary study on gas metal arc welding-based additive manufacturing of metal parts

Introduction: In the past three decades, additive manufacturing (AM), also known as 3D printing, has emerged as a promising technology, which allows the manufacture of complex parts by adding material layer upon layer. In comparison, with other metal-based AM technologies, gas metal arc welding-based additive manufacturing (GMAW-based AM) presents a high deposition rate and has the potential for producing medium and large metal components. To validate the technological performance of such a manufacturing process, the internal quality of manufactured parts needs to be analyzed, particularly in the cases of manufacturing the parts working in a critical load-bearing condition. Therefore, this paper aims at investigating the internal quality (i.e., and mechanical properties) of components manufactured by the GMAW-based AM technology.
 Method: A gas metal arc welding robot was used to build a thin-walled component made of mild steel on a low-carbon substrate according to the AM principle. Thereafter, the specimens for observing and mechanical properties were extracted from the built thin-walled component. The of the specimen were observed by an optical microscope; the hardness was measured by a digital tester, and the tensile tests were carried out on a tensile test machine.
 Results: The results show that the GMAW-based AM-built thin-walled components possess an adequate that varies from the top to the bottom of the built component: structures with primary dendrites in the upper zone; granular structure of with small regions of at grain boundaries in the middle zone, and grains of in the lower zone. The hardness (ranged between 164±3.46 HV to 192±3.81 HV), yield strength (YS offset of 0.2% ranged from 340±2 to 349.67±1.53 ), and ultimate tensile strength (UTS ranged from 429±1 to 477±2 ) of the GMAW-based AM-built components were comparable to those of wrought mild steel.
 Conclusions: The results obtained in this study demonstrate that the GMAW-based AM-built components possess adequate and good mechanical properties for real applications. This allows us to confirm the feasibility of using a conventional gas metal arc welding robot for additive manufacturing or repairing/re-manufacturing of metal components.

Effect of deposition orientations on dimensional and mechanical properties of the thin-walled structure fabricated by tungsten inert gas (TIG) welding-based additive manufacturing process

Welding-based additive manufacturing can potentially produce a cost-effective process for the production of dense metallic parts. Tungsten inert gas (TIG) welding-based additive manufacturing process uses wire as a filler material and offers a high deposition rate with low spattering. In this study, different orientations of wire feeding nozzle and TIG welding torch, such as front wire feeding (FWF), back wire feeding (BWF), and side wire feeding (SWF), were investigated for thin-walled metal deposition with enhanced dimensional accuracy and mechanical properties. The dimensional accuracy of thin-walls deposited at four different orientations were investigated in terms of deposition height and deposition width. The FWF orientation with higher wire feeding angle and SWF orientation produced poor dimensional accuracy in the deposition. FWF orientation with normal wire feeding angle and BWF orientation provided a decent dimensional accuracy and surface appearance. The deposited samples exhibited a similar trend for Vickers microhardness, residual stress, and microstructure for the four different wire feeding orientations.

Thin-walled metal deposition with GTAW welding-based additive manufacturing process

The arc welding-based additive manufacturing technology is in its developing state. This technology can be utilized to produce free-form metallic structures for the aerospace and biomedical industry. The current article presents the design of semi-automatic gas tungsten arc welding-based additive manufacturing system for fabricating thin-walled metallic structures. This study aims to analyze the effect of process variables on the output parameters, such as deposition width and deposition height. The set of experiments were performed based on the design developed by Taguchi method. The experimental data have been analyzed to study the effect of the significant process parameters like current, torch speed, wire feeding speed and torch angle. The optimization of the significant process parameters has been done to ensure thin-walled deposition with minimum wall thickness and better geometric characteristics. Experimental results showed that as the angle of inclination increases the deposition width increases and the deposition height decreases. The surface appearance of the bead sample deposited at a different angle of inclination was investigated. The thickness of the wall obtained in this study was found to be the lowest wall thickness achieved by the arc welding-based additive manufacturing process deploying filler material of 1.2 mm diameter.

The formation and Kr-ion irradiation behaviour of new microstructural features in additively manufactured titanium aluminium alloy

New microstructural features were found in the TiAl alloy manufactured using the gas tungsten arc welding-based additive manufacturing technology. The ion-irradiation responses of the new microstructure features were investigated in-situ via irradiation with 1 MeV Kr2+ ions at room and 873 K. Examination of the microstructure showed that the typical lamellar microstructure consisting of α2-Ti3Al and γ-TiAl phases formed α2/γ lamellar interfaces and γ/γ twin boundaries. Apart from this, the γ lamellae were also found to form γ/γ lamellar boundaries with the two γ lamellae in the same orientation or the <10-1 > //<411> orientation relationship. This is not observed in the TiAl alloys fabricated using traditional alloy fabrication methods. Kr ion-irradiation at room and elevated temperatures resulted in no significant difference in the morphologies of most radiation-induced defects in the <411> orientated γ lamellae and the <10-1> orientated γ lamellae. However, the areas of the new boundaries exhibited different damage morphologies in comparison with the traditional γ/γ twin boundaries. The formation mechanisms of the new microstructural features formed in the additive manufacturing process and their irradiation behaviour are investigated and discussed.

THE APPLICATION OF WELD-BASED ADDITIVE MANUFACTURING STEEL TO STRUCTURAL ENGINEERING

The present work aims at providing the first considerations upon the application of innovative manufacturing technology for civil engineering purposes. In particular, among the 3D printing processes currently available, Weld-Based Additive Manufacturing (WAM) results to be the most suitable technique for the realization of innovative structural forms in metal material. The great potential of taking the printing head "out of the box" allows for the construction of innovative shapes by adding layer upon layer of welded steel. In particular, the study is focused on the realization of the first 3D-printed steel footbridge by a Dutch company held in Amsterdam, called MX3D, and its Additive manufacturing process, which results in specific constraints and limitations to be taken into account for design purposes. First, the design issues are described, by considering the printing parameters to be adopted for the realization of large-dimensions structures, and then the implications in terms of specific geometrical and mechanical characteristics are studied. These first engineering evaluations are intended to pave the way towards the development of a ground-breaking technology for the fully-automated design and construction of novel 3D-printed building structures through innovative robotic manufacturing processes whose parameters are still not fully known

Twin-wire welding based additive manufacturing (TWAM): manufacture of functionally gradient objects

PurposeTwin-wire welding-based additive manufacturing (TWAM) is a unique process which uses gas metal arc welding (GMAW)-based twin-wire weld-deposition to create functionally gradient materials (FGMs). Presented study aims to focus on creating metallic objects with a hardness gradient using GMAW of twin-wire weld deposition setup.Design/methodology/approachBy using dissimilar filler wires in twin-wire weld-deposition, it is possible to create metallic objects with varying hardness. This is made possible by individually controlling the proportion of each filler wire used. ER70S-6 and ER110S-G are the two filler wires used for the study; the former has lower hardness than the latter. In the current study, methodology and various experiments carried out to identify the suitable process parameters at a given location for a desired variation of hardness have been presented. A predictive model for obtaining the wire speed of the filler wires required for a desired value of hardness was also created. Subsequently, sample parts with gradient in various directions have been fabricated.FindingsFor dissimilar twin-wire weld-deposition used here, it is observed that the resultant hardness is in the volumetric proportion of the hardness of the individual filler wires. This aids the fabrication of FGMs using arc based weld-deposition with localized control of hardness, achieved through the control of the ratio of wire speeds of the individual filler wires. Four sample parts were fabricated to demonstrate the concept of realizing FGMs through TWAM. The fabricated parts showed good match with the desired hardness variation.Research limitations/implicationsThis paper successfully presents the capability of TWAM for creating gradient metallic objects with varying hardness. Although developed using ER70S-6 and ER110S-G filler wire combination, the methodology can be extended for other filler wire combinations too for creating FGMsOriginality/valueGMAW-based twin-wire welding for additive manufacturing is a novel process which uses dissimilar filler wires for creating FGMs. This paper describes methodology of the same followed by illustration of parts created with bi-directional hardness gradient.