Arc-based Additive Manufacturing Research Articles

Wire and arc-based additive manufacturing of 316L SS: predicting and optimizing process variables using BRFFNN, NSGA-GP and TOPSIS approach

Wire and arc-based additive manufacturing of 316L SS: predicting and optimizing process variables using BRFFNN, NSGA-GP and TOPSIS approach

Microstructural and Mechanical Properties of Nickel-Based Superalloy Fabricated by Pulsed-Mode Arc-Based Additive Manufacturing Technology

Microstructural and Mechanical Properties of Nickel-Based Superalloy Fabricated by Pulsed-Mode Arc-Based Additive Manufacturing Technology

Residual Stresses in a Wire and Arc-Directed Energy-Deposited Al–6Cu–Mn (ER2319) Alloy Determined by Energy-Dispersive High-Energy X-ray Diffraction

In order to enable and promote the adoption of novel material processing technologies, a comprehensive understanding of the residual stresses present in structural components is required. The intrinsically high energy input and complex thermal cycle during arc-based additive manufacturing typically translate into non-negligible residual stresses. This study focuses on the quantitative evaluation of residual stresses in an Al–6Cu–Mn alloy fabricated by wire and arc-directed energy deposition. Thin, single-track aluminum specimens that differ in their respective height are investigated by means of energy-dispersive high-energy X-ray diffraction. The aim is to assess the build-up of stresses upon consecutive layer deposition. Stresses are evaluated along the specimen build direction as well as with respect to the lateral position within the component. The residual stress evolution suggests that the most critical region of the specimen is close to the substrate, where high tensile stresses close to the material’s yield strength prevail. The presence of these stresses is due to the most pronounced thermal gradients and mechanical constraints in this region.

Properties oriented WAAM—microstructural and geometrical control in WAAM of low-alloy steel

Today, arc-based additive manufacturing has great potential for industrial application due to new developments in robotics, welding technology, and computer-aided manufacturing. Two issues are currently the focus of research. One is the accurate generation of geometry with respect to the design, e.g., geometry fidelity, defined roughness, and shape deviations within the tolerances. Here, there are still open questions, particularly with regard to path planning and the dependence of the geometry on the selected process variables. The second topic is the adjustment or determination of the achievable mechanical and microstructural properties, as these are of crucial importance for the use of the technology in industry. The combination of both areas into a geometry- and property-oriented approach to additive manufacturing has been little discussed in the literature for arc-based welding processes. The correlations between cooling conditions and emerging properties can serve as a starting point for such a consideration. The temperature history depends on three key factors: the energy input, the interpass temperature (which in additive manufacturing is determined by the time to over-weld), and the heat transfer conditions, which are determined by the part geometry. The melt pool size or volume also depends on these three constraints. In this study, an approach is presented to realize property-oriented additive manufacturing from the interaction of property-oriented path planning and a melt pool size control system. By controlling the melt pool size, the cooling of the material can be adjusted within certain limits, and consequently, a local adjustment of the microstructure can be achieved, which greatly influences the local mechanical properties. This work demonstrates this approach for a low-alloy filler metal (DIN EN ISO 14341-A G 50 7 M21 4Mo/A5.28 ER80S-D2). Gas metal arc welding was carried out using an M21 shielding gas (82% Ar, 18% CO2). Finally, microstructural characterization will show that different microstructural morphologies and properties can be achieved in a component by combining property-oriented path planning and the use of a control loop to regulate the melt pool size.

Plasma powder transferred arc additive manufacturing of ((Fe, Ni)-Al) intermetallic alloy and resulting properties

Intermetallic alloys such as iron aluminides are of increasing interest for high-temperature applications due to their properties. However, their application potential is restricted by their limited machinability with conventional manufacturing methods such as milling. Arc-based additive manufacturing offers an approach to produce these materials to final contour or with very little post-processing. However, the properties of many intermetallic alloys, such as low toughness, require a special manufacturing process. Using a selected iron-nickel-aluminum intermetallic compound as an example, a possible process, including a subsidiary heat treatment, for the arc-based additive manufacturing of materials based on brittle intermetallic materials is presented. This process route could enable the production of structural components. In addition, some basic mechanical properties that can be achieved in a component are shown proportionally. These properties include initial investigations into the wear resistance of this kind of compounds. It is shown that these intermetallic compounds have a superior wear resistance compared to commonly used co-base alloys but have a lower density compared to cobalt-basis alloys.

Numerical investigation of the arc behaviour and air transport during pulsed tungsten inert gas arc-based additive manufacturing

Numerical investigation of the arc behaviour and air transport during pulsed tungsten inert gas arc-based additive manufacturing

Wire‐and‐Arc Additive Manufacturing for lattice steel structures: overview of the experimental characterization on dot‐by‐dot rods

AbstractWith the advent of a new arc‐based additive manufacturing (AM) process, referred to as Wire‐and‐Arc Additive Manufacturing (WAAM), the scale of the metal printed parts increased up to several meters, thus becoming suitable for large‐scale applications in marine, aerospace and construction sectors. However, specific considerations in terms of geometrical and mechanical properties ought to be made in order to effectively use the printed outcomes for structural engineering purposes. The introduction of the novel printing strategy referred to as “dot‐by‐dot”, consisting in successive drops of molten metal, enabled the use of WAAM to realize complex lattice structures, made by continuous grids of WAAM rods. Nevertheless, their proper design requires an accurate evaluation of the influence of the non‐negligible inherent geometrical irregularities on the mechanical response of the rods. Hence, extensive experimental work is needed in order to evaluate the mechanical response of “dot‐by‐dot” WAAM rods with geometrical imperfections. The present study focuses on the mechanical characterization of dot‐by‐dot WAAM‐produced 304L stainless steel intersected rods, constituting the basic units of grid and lattice structures. The mechanical response of the specimens is assessed through tensile experimental tests conducted on two‐ways planar nodes obtained from the intersection of two rods with different angles, hereafter also refereed to as crossed rods. The experimental results are then compared with tensile tests on single rods, to quantify the influence of the intersection angle in the structural response of the lattice structures.

Local control of microstructure and mechanical properties of high-strength steel in electric arc-based additive manufacturing

Additive manufacturing offers a significant potential for producing metallic parts with distinctly localised microstructures and mechanical properties, commonly known as functional grading. While functional grading is generally accomplished through compositional variations or in-situ thermo-mechanical treatments, variation of process parameters during additive manufacturing can offer a promising alternative approach. Focusing on the electric arc-based additive manufacturing process, this work focuses on the functional grading of high-strength steel (S690 grade) by adjusting the travel speed and inter-pass temperature. Through a combination of thermal simulations and experimental measurements on single bead-on-plate depositions, it is shown that the microstructure and the mechanical properties of parts can be controlled through the rational adjustment of process parameters. A rectangular block was fabricated to demonstrate functional grading using a constant wire feed rate and varying travel speed. The rectangular block consisted of a low heat input (LHI) region deposited between high heat input (HHI) zones. A graded microstructure was obtained with the HHI zones composed of a mixture of polygonal ferrite, acicular ferrite, and bainite, while the LHI region was primarily composed of martensite. The hardness and profilometry-based indentation plastometry measurements indicated that the LHI region exhibited higher hardness (32%) and strength (50%), but lower uniform elongation (80%), compared to the HHI zones. The present study demonstrates the potential to achieve functional grading by adjusting process parameters in electric arc-based additive manufacturing, providing opportunities for tailor-made properties in parts.

Special Issue on Recent Trends in Additive Manufacturing

Additive manufacturing (AM) has undergone rapid development in the past decade. Owing to its capacity to produce complex and functional parts in various industries, it has been recognized as a remarkable scientific and industrial technique. It is used to enhance weight-saving production and reduce the number of parts, with metal-based AM techniques in particular being recognized as the most promising AM techniques developed thus far. This is because of their high potential for direct production through the selective solidification of metal materials from three-dimensional, computer-aided design data. The medical, aerospace, and part molding industries are some of the many expected to reap particular benefit from the ability to produce high-quality models with reduced manufacturing costs and lead times. The objective of this special issue is to collect recent research works focused on recent trends in AM. This issue includes 7 papers covering the following topics: - Metal-based powder bed fusion using a laser beam (PBF-LB/M) - Wire and arc-based AM (WAAM) - Fused deposition modeling (FDM) This special issue is expected to help readers understand the recent trends in AM, leading in turn to further research on AM. We deeply appreciate the contributions of all authors and thank the reviewers for their incisive efforts.

Effects of thermal history of in-situ thermal management on as-built property heterogeneity of plasma arc additively manufactured Inconel 625

In-situ thermal management (ISTM) is one of the most prospective approaches to alleviating heat accumulation and achieving progressive forming for arc-based additive manufacturing. The aim of this study was to investigate the influences of thermal history, i.e., the cooling rate and the intrinsic heat treatment (IHT), of ISTM on as-built property heterogeneity of plasma arc additively manufactured Inconel 625 thin-wall deposit. The thermal history is obtained from numerical simulation. Results show that the variation of the thermal history of ISTM results in the bottom-up varied cooling rate and IHT, which together lead to the location-heterogeneous primary dendrite arm spacing, interdendritic phases and grain size. IHT of each layer is quantified by temperature-time integration (TTI), and Gaussian distributed TTI (above 600 °C) indicates the middle region of the deposit with ISTM is subjected to the most intense IHT. Compared with the counterpart of the conventional interlayer cooling strategy, the intensified high-temperature IHT of ISTM contributes to significant mitigation of micro-segregation, i.e., the brittle-hard interdendritic phases reduce 61.9%. Furthermore, a weighted value of cooling rate and TTI is innovatively introduced to depict the heterogeneity of mechanical property, which presents an exponential growth of ultimate tensile strength with the weighted value. Moreover, the layer-by-layer decreased heat input and the high-temperature preheating between layers of ISTM contribute to a certain residual stress release effect along the building direction.

Fabricating TiAl alloys with various compositions by twin-wire arc AM

ABSTRACT TiAl alloys with different Al atomic compositions, i.e. Ti45Al, Ti48Al, and Ti51Al, were produced via double-wire arc-based additive manufacturing by altering the aluminum wire feed rate. The microstructure and mechanical performance of deposited parts were researched. By changing the aluminum composition from 45 at% to 51 at%, the microstructure in the uniform area transforms from equiaxed α2/γ lamellar and near-lamellar colonies to dual-phase structures and near-lamellar colonies, the volume fraction of α2 phase decreases from 46.5% to 12.4%, and the total microhardness decreases from 411 to 356 HV. As the aluminum composition increases, the compressive strength presents an increasing trend first and then a decreasing trend, and the compressive ratio presents an increasing trend. The maximum compressive strength and compressive ratio in the vertical and horizontal orientations are 1822.5 MPa, 1732.5 MPa, 19.9%, and 20.2%, respectively.

Microstructure, deformation and fracture mechanisms in Al-4043 alloy produced by laser hot-wire additive manufacturing

High deposition rate additive manufacturing (AM) processes with minimal feedstock costs are desirable to reduce part fabrication times and minimize the cost of implementation. Wire-based AM processes meet these demands but suffer from higher heat inputs that can lead to thermal distortion and large heat-affected zones neighboring the melt pools. Here, the tensile deformation response of an Al 4043 (Al-Si) alloy deposited on an Al 6061-T6 substrate using a laser hot-wire AM process was investigated. Digital image correlation during tensile testing was combined with optical microscopy and electron backscatter diffraction data to understand the deformation mechanisms that occurred in samples from a deposited wall in the as-built condition. During tensile testing, localized deformation was observed at the melt pool boundary regions that correlated with serrations on the stress-strain curve. The primary aluminum dendrites in regions adjacent to the melt pool boundary regions were coarser than in bulk deposited material, leading to localized deformation of the coarser microstructure. EBSD post-test analysis confirmed that the accumulated strains had occurred in the melt pool boundary regions. Analysis of the thermal and solidification conditions in the melt pool indicated that the coarsened region was associated with partial remelting of the eutectic phase. This understanding of deformation mechanisms associated with the inhomogeneities at melt pool boundaries can enable AM-specific considerations for improved process and alloy design, particularly for eutectic alloys. • Al 4043 parts were deposited using laser hot-wire additive manufacturing. • The deposited Al 4043 had similar mechanical properties to arc-based AM. • DIC during tensile testing revealed serrated flow resulting from localized deformation. • Partial remelting of the eutectic near the melt pool boundary resulted in coarser dendrites than bulk regions. • Localized deformation was correlated with the coarser microstructure near the melt pool boundary.

A numerical model-based deposition strategy for heat input regulation during plasma arc-based additive manufacturing

Heat accumulation in metal additive manufacturing (AM) processes leads to the unstable molten pool size, nonuniform track morphology, excessive dilution, and even structural collapse. Therefore, appropriate heat input management to alleviate heat accumulation is critical for metal AM processes. In order to mitigate heat accumulation and achieve better geometric accuracy, this work develops an innovative 3D numerical model-based deposition strategy to regulate the heat input for the metal AM process. Specifically, the proposed deposition strategy involves two steps: (i) a thermal simulation of the deposition process via an intelligent heat source tracking algorithm, thereby outputting a series of heat source data to ensure a constant molten pool size of the 3D model, and (ii) the output heat source data are utilized to regulate the heat input point-by-point of the deposit in the subsequent AM process. The proposed deposition strategy is demonstrated for plasma arc-based additive manufacturing (PA-AM) of a 20-layer Inconel 625 thin-walled deposit. The surface quality is measured with a profiler and the deviation of the deposits in the building direction is calculated by image processing techniques. The results show that the proposed deposition strategy is superior in geometric accuracy compared with the conventional approaches (i.e., the introduction of interlayer dwell time) from the perspectives of the forming height, surface morphology, and vertical deviation in the building direction. Meanwhile, benefitting from progressive forming and thermal management, PA-AM through the proposed approach can significantly reduce the total deposition time and energy consumption.

Evaluation of Cu-Ti dissimilar interface characteristics for wire arc additive manufacturing process

PurposeThe purpose of this research is to show the characteristics of a Cu–Ti dissimilar interface produced by a wire arc-based additive manufacturing process. The purpose of this research was to determine the viability of the Cu–Ti interface for the fabrication of functionally graded structures (FGS) using the wire arc additive manufacturing (WAAM) process.Design/methodology/approachThis paper used the WAAM process with variable current vis-à-vis heat input to demonstrate multiple Ti-6Al-4V (Ti64) and C11000 dissimilar fabrications. The hardness and microstructure of the dissimilar interfaces were investigated thoroughly. The formation of Cu–Ti intermetallic at the Ti64/Cu fusion interface is been revealed by scanning electron microscopy and energy dispersive X-ray analysis, while X-ray diffraction was used to identify various Cu–Ti intermetallic phases. The effect of microstructure on interfacial sensitivity and hardness are also investigated.FindingsThe formation of CuTi intermetallic and the β-phase transformation in Ti-6Al-4V are found to be heat input dependent. The Cu diffusion length increases as the heat input for Ti64 deposition increases, resulting in a greater Cu–Ti intermetallic thickness. The Cu–Ti interface properties improve when the heat input is less than approximately 250 J/mm or the deposition current is less than 90 A. The microhardness ranges from 55 to 650 HV from the Cu-side to the interface and from 650 to 350 HV from the interface to the Ti-side. Higher current increases interface hardness, which increases brittleness and makes the interface more prone to interfacial cracking.Originality/valueNonlinear components are needed for a variety of extreme engineering applications, which can be met by FGS with varying microstructure, composition and properties. FGS produced using the WAAM process is a novel concept that requires further investigation. Despite numerous studies on Ti-clad Cu, information on Cu–Ti interface characteristics is lacking. Furthermore, the suitability of the WAAM process for the development of Cu–Ti FGS is unknown. As a result, the goal of this research article is to fill these gaps by providing preliminary information on the feasibility of developing Cu–Ti FGS via the WAAM process.

A novel methodology to manufacture complex metallic sudden overhangs in weld-deposition based additive manufacturing

PurposeAmongst various additive manufacturing (AM) techniques for realizing the complex metallic objects, weld-deposition (arc)-based directed energy AM technique is attaining more focus over commercially available powder bed fusion techniques. This is because of the capability of high deposition rates, high power and material utilization, simpler setup and less initial investment of arc-based AM. Nevertheless, realization of sudden overhanging features through arc-based weld-deposition techniques is still a challenging task because of the necessity of support structures. This paper aims to describe a novel methodology for producing complex metallic objects with sudden overhangs without using supports.Design/methodology/approachThe realization of complex metallic objects with sudden overhangs (without using supports) is possible by reorienting the workpiece and/or deposition head at every instance using higher order kinematics (5-axis setup) to make sure the overhanging feature is in line to the deposition direction.FindingsIn the absence of universally applicable support mechanism, deposition of overhanging features remains one of the main challenges in AM. A separate support structure is often necessary for depositing the overhanging features. Small overhang features are usually possible by a little overextension from the previous layer. Nevertheless, deposition of large gradually varying overhangs and sudden overhangs with complex features without support structures is a challenging task in any AM process. This demands higher order kinematics which calls for inclined and/or orthogonal slicing and area filling.Originality/valueThe unique aspect of this paper is the identification of sudden overhang feature from a tessellated computer-aided design (.stl) file and generates an orthogonal tool path for deposition for sudden overhangs. An in-house MATLAB routine has been developed and presented for performing the same. This methodology helps in realization of sudden overhangs without use of supports. To validate proposed technique, various illustrative case studies have been taken up for deposition.

Development of an Alternative Alloying Concept for Additive Manufacturing Using PVD Coating

New alloys are needed to adapt the material properties and to improve the weldability of arc-based additive manufacturing processes. The classic development of welding filler materials is time-consuming and cost-intensive. For this reason, an alternative alloy concept is investigated and qualified here. This is based on the thin-film coating of welding filler materials by means of PVD coating. An HSLA steel DIN EN ISO 14341-A G 50 7 M21 is used as the base material. This is alloyed with the elements Al, Cr, Nb, Ni and Ti by means of PVD thin-film coating. This procedure represents an alternative alloy concept. In the scope of the qualification, the influence of the process and material properties is investigated, and the alternative alloying concept is compared with the classical alloying concept of secondary metallurgy. The investigations have shown that the thin film coating on the surface of the welding filler metal affects the process properties in the form of a changed arc length. Furthermore, the mechanical properties and the effect on the microstructure morphology were investigated. These were compared in the same chemical composition with a Mn4Ni2CrMo produced by secondary metallurgy. The results are in agreement with regard to the mechanical properties and the effect on the microstructure morphology.

Wire and Arc Additive Manufacturing of a CoCrFeMoNiV Complex Concentrated Alloy Using Metal-Cored Wire—Process, Properties, and Wear Resistance

The field of complex concentrated alloys offers a very large number of variations in alloy composition. The achievable range of properties varies greatly within these variants. The experimental determination of the properties is in many cases laborious. In this work, the possibility of using metal-cored wires to produce sufficient large samples for the determination of the properties using arc-based additive manufacturing or in detail wire and arc additive manufacturing (WAAM) is to be demonstrated by giving an example. In the example, a cored wire is used for the production of a CoCrFeNiMo alloy. In addition to the process parameters used for the additive manufacturing, the mechanical properties of the alloy produced in this way are presented and related to the properties of a cast sample with a similar chemical composition. The characterization of the resulting microstructure and wear resistance will complete this work. It will be shown that it is possible to create additively manufactured structures for a microstructure and a property determination by using metal-cored filler wires in arc-based additive manufacturing. In this case, the additively manufactured structure shows an FCC two-phased microstructure, a yield strength of 534 MPa, and a decent wear resistance.

Feedback control of variable width in gas metal arc-based additive manufacturing

Gas metal arc additive manufacturing (GMA-AM) is one of the most promising methods to produce large-scale complex metal parts by melting metal wire layer by layer. Nevertheless, this process is prone to be affected by various disturbances and requires online monitoring and feedback control. This study aims at fabricating variable-width components in which layer width in the same layer is changeable in GMA-AM via an in-situ monitoring and control system. A passive vision sensing system, composed of a camera and a biprism, was designed to extract the layer width in real-time via the procedures of camera calibration, image correction, molten pool extraction, and molten pool edge reconstruction. A fuzzy controller was designed by adjusting the arc current to maintain the expected layer width. The controller's performance was verified by performing inter-layer temperature and travel speed disturbance tests. Two 20-layered variable-width walls were built, and the results demonstrate that the passive vision sensing and feedback control system can significantly improve the layer width stability.

Modelling and optimization of weld bead geometry in robotic gas metal arc-based additive manufacturing using machine learning, finite-element modelling and graph theory and matrix approach

Modelling and optimization of weld bead geometry in robotic gas metal arc-based additive manufacturing using machine learning, finite-element modelling and graph theory and matrix approach

Residual Stress and Distortion in Gas Metal Arc-Based Additive Manufacturing

Residual Stress and Distortion in Gas Metal Arc-Based Additive Manufacturing