Additive manufacturing has revolutionized the manufacturing paradigm in recent years due to the possibility of creating complex shaped three-dimensional parts which can be difficult or impossible to obtain by conventional manufacturing processes. Among the different additive manufacturing techniques, wire and arc additive manufacturing (WAAM) is suitable to produce large metallic parts owing to the high deposition rates achieved, which are significantly larger than powder-bed techniques, for example. The interest in WAAM is steadily increasing, and consequently, significant research efforts are underway. This review paper aims to provide an overview of the most significant achievements in WAAM, highlighting process developments and variants to control the microstructure, mechanical properties, and defect generation in the as-built parts; the most relevant engineering materials used; the main deposition strategies adopted to minimize residual stresses and the effect of post-processing heat treatments to improve the mechanical properties of the parts. An important aspect that still hinders this technology is certification and nondestructive testing of the parts, and this is discussed. Finally, a general perspective of future advancements is presented.

Current Status and Perspectives on Wire and Arc Additive Manufacturing (WAAM)

In the circular economy, products, components, and materials are aimed to be kept at the utility and value all the lifetime. For this purpose, repair and remanufacturing are highly considered as proper techniques to return the value of the product during its life. Directed Energy Deposition (DED) is a very flexible type of additive manufacturing (AM), and among the AM techniques, it is most suitable for repairing and remanufacturing automotive and aerospace components. Its application allows damaged component to be repaired, and material lost in service to be replaced to restore the part to its original shape. In the past, tungsten inert gas welding was used as the main repair method. However, its heat affected zone is larger, and the quality is inferior. In comparison with the conventional welding processes, repair via DED has more advantages, including lower heat input, warpage and distortion, higher cooling rate, lower dilution rate, excellent metallurgical bonding between the deposited layers, high precision, and suitability for full automation. Hence, the proposed repairing method based on DED appears to be a capable method of repairing. Therefore, the focus of this study was to present an overview of the DED process and its role in the repairing of metallic components. The outcomes of this study confirm the significant capability of DED process as a repair and remanufacturing technology.

Application of Directed Energy Deposition-Based Additive Manufacturing in Repair

Remanufacturing is one of the critical elements moving our economy toward one that is circular. Today, remanufacturing is attracting growing attention worldwide. Meanwhile, despite its potential in terms of its effects on both environment and economy, remanufacturing has not yet been sufficiently exploited. This indicates that there exist both drivers for and barriers to an increase in remanufacturing in economies. Although there are both technological and non-technological requirements for remanufacturing, R&D is unavoidable for its promotion. This article outlines trends, drivers, and barriers for remanufacturing, and presents reviews of studies on selected topics in remanufacturing. The selected R&D topics in this article are product design for remanufacturing, additive manufacturing for remanufacturing, operations management in remanufacturing, and business models for remanufacturing.

Trends and research challenges in remanufacturing

Additive layer manufacturing (ALM), using gas tungsten arc welding (GTAW) as heat source, is a promising technology in producing Inconel 625 components due to significant cost savings, high deposition rate and convenience of processing. With the purpose of revealing how microstructure and mechanical properties are affected by the location within the manufactured wall component, the present study has been carried out. The manufactured Inconel 625 consists of cellular grains without secondary dendrites in the near-substrate region, columnar dendrites structure oriented upwards in the layer bands, followed by the transition from directional dendrites to equiaxed grain in the top region. With the increase in deposited height, segregation behavior of alloying elements Nb and Mo constantly strengthens with maximal evolution in the top region. The primary dendrite arm spacing has a well coherence with the content of Laves phase. The microhardness and tensile strength show obvious variation in different regions. The microhardness and tensile strength of near-substrate region are superior to that of layer bands and top region. The results are further explained in detail through the weld pool behavior and temperature field measurement.

Effect of location on microstructure and mechanical properties of additive layer manufactured Inconel 625 using gas tungsten arc welding

Wire and arc additive manufacturing : Opportunities and challenges to control the quality and accuracy of manufactured parts

Causes of failure and repairing options for dies and molds: A review

Development of micro-plasma transferred arc (μ-PTA) wire deposition process for additive layer manufacturing applications

The realization of microwave's heating ability is a significant discovery in the history of scientific research. The thermal ability of microwave has led to the invention of devices and processes that could replace conventional heating methods and reduce humankind's dependency on fossil fuels. In the early days, microwave heating was limited to food processing and drying. Researchers over the years have examined the utility of microwave in materials processing and showed encouraging outcomes. Currently, microwave-based materials processing research is aligned toward exploring the processing of novel materials and achieving greater reliability and control in the existing processes. This, in turn, requires extensive knowledge of the parameters of the microwave heating processes. This review provides insights into microwave-based heating parameters and their effect on the response parameters of major microwave processing applications. Four significant parameters viz., heating mechanisms, dielectric and magnetic properties, load and applicators have been identified and factors influencing these parameters have been critically examined to understand the requirements of efficient microwave-based materials processing. This review analyzes the existing state of research and identifies the future scope of research in this field. It reveals optimization studies, commercialization of the process at large scale, simulation studies for better understanding of heating mechanisms and innovation in processing set-ups as few of the potential areas with a wide scope for investigation.

Parametric review of microwave-based materials processing and its applications

Micro-plasma transferred arc (µPTA) additive manufacturing is one of the newest options for remanufacturing of dies and molds surfaces in the near-millimeter range leading to extended usage of the same. We deployed an automatic micro-plasma deposition setup to deposit a wire of 300 µm of AISI P20 tool steel on the substrate of same material for the potential application in remanufacturing of the die and mold surface. Our present research effort is to establish µPTA additive manufacturing as a viable economical and cleaner methodology for potential industrial applications. We undertook the optimization of single weld bead geometry as the first step in our present study. Bead-on-plate trials were conducted to deposit single bead geometry at various processing parameters. The bead geometry (shape and size) and dilution were measured and the parametric dependence was derived. A set of parameters leading to reproducible regular and smooth single bead geometry were identified and used to prepare a thin wall for mechanical testing. The deposits were subjected to material characterization such as microscopic studies, micro-hardness measurements and tensile testing. The process was compared qualitatively with other deposition processes involving high-energy density beams and was found to be advantageous in terms of low initial and running costs with comparable properties. The outcome of the study confirmed the process capability of µPTA deposition leading to deployment of cost-effective and environmentally friendlier technology for die and mold remanufacturing.

Micro-Plasma Transferred Arc Additive Manufacturing for Die and Mold Surface Remanufacturing

Micro-plasma-transferred arc (µPTA) wire deposition is a cost-effective additive layer manufacturing process used for remanufacturing/repair of high-value components. Prediction of geometry and cross-sectional area of each deposition track and deposition overlap between the successive deposition tracks helps in optimizing the deposition strategies and automated repair and remanufacturing of the components by µPTA process. This paper presents investigations on enhancing the deposition quality in µPTA process by approximating deposition geometry as an elliptical arc with an objective to predict its cross-sectional area and to optimize the deposition overlap between the successive deposition tracks. The model was validated using the experimental apparatus developed for the µPTA wire deposition process. The predictions were compared with the previously developed models of deposition geometry considering it as an arc of parabola, circle, and cosine function. The results proved the superiority of the elliptical...

Suyog Jhavar

Papers

Causes of failure and repairing options for dies and molds: A review

Development of micro-plasma transferred arc (μ-PTA) wire deposition process for additive layer manufacturing applications

Parametric review of microwave-based materials processing and its applications

Micro-Plasma Transferred Arc Additive Manufacturing for Die and Mold Surface Remanufacturing

Enhancement of Deposition Quality in Micro-plasma Transferred Arc Deposition Process