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Wire arc additive manufacturing (WAAM), also known as Arc-DED, possesses great potential for efficient production using various materials and wire types. This study utilized gas metal arc (GMA) and plasma transferred arc (PTA) variants of WAAM to deposit 2.25Cr-1Mo steel employing a metal-cored wire (MCW) and a solid wire counterpart having the same chemical composition for the comparative study. Initially, bead-on-plate trials were conducted with both WAAM processes and different shielding gas combinations in GMA-WAAM using the cored wire. The heat input versus deposition ratio was analysed to assess the heat input and the effects of shielding gases in GMA-WAAM. Arc behaviour was monitored with a process camera, and bead morphologies and dilutions were compared. Furthermore, test walls were deposited under the two WAAM processes and the shielding gas conditions, employing the cored and solid wire. Detailed microstructural study was conducted through optical microscopy, and hardness tests were performed to determine the mechanical properties. Energy dispersive X-ray spectroscopy (EDS) was used to examine the elemental composition and potential segregation in walls deposited with cored and solid wires. Results indicated a lower heat input when using cored wire and variable heat input due to shielding gases. A bainitic/martensitic microstructure was observed in test walls deposited with cored and solid wires with comparable microstructural features. The PTA process produced higher hardness than GMA, and solid wire exhibited slightly higher hardness than cored wire. Selection of shielding gas also influenced the hardness. Finally, the EDS maps and elemental study revealed comparable results for both wires. The results show good performance and outcome for cored wire.

Recently, dieless forming processes have been introduced to prevent the high costs of dies and tools. Local heating and axial compression process is an innovative method for producing metal bellows. In this research, producing metal bellows using simultaneous local electric arc heating and axial compression has been explained and investigated. SUS304 tubes with an outer diameter of 19 mm and a thickness of 1 mm have been employed to implement the tests. Various parameters could affect the process. Among these parameters, effects of applied displacement and device current, influencing convolution shape, thickness, and required forming force, are studied experimentally. It is found that the height, radius, and angle of the convolution and also the forming force could be controlled by alteration of these parameters. Furthermore, the result of buckling test showed that energy absorption capacity of the manufactured metal bellow has been increased in comparison to a typical tube. This method could be a suitable alternative for induction local heating and can reduce the high equipment costs.

The effective welding of a 6 mm thick TA2 pure titanium medium-thickness plate was achieved by laser–arc hybrid welding (LAHW) with helium–argon mixed shielding gas. Conducted research on the influence of helium–argon mixed shielding gas on plasma and arc characteristics during welding, and its further impact on the microstructure, internal porosity defects, tensile properties, and corrosion resistance of welded joints was explored. The study demonstrated that under the shielding gas with 75% helium, the arc width narrowed significantly from 6.96 mm to 2.61 mm, achieving a 63% reduction, which enhanced the concentration of arc heat flux density. Achieved a well-formed weld with no surface spatter and significantly reduced the internal porosity rate from 3.02% to 0.47%, which is an 84% decrease. Tensile fractures are located in the base material, all exhibiting plastic failure. The corrosion resistance of the welded joint initially increased and then decreased with the increase of helium content in the shielding gas, peaking at 75% helium content.

The results of experimental studies concerning the plasma fusing of wear-resistant coatings on the worn surfaces of hollow parts serving as bodies of revolution. The influence of the plasmatron arc heat flux on the thermal cycle of the deposited wear-resistant coating is substantiated experimentally. For the coating deposition, we took a mixture of compressed air and hot hydrocarbons as the plasma-forming gas. We show experimentally that, in order to select the optimal thermal cycle of plasma fusing and to obtain the desired mechanical properties of the applied wear-resistant coating, we should change the parameters of the plasma fusing mode. Here, the plasmatron oscillation amplitude influences the recovered part of the temperature. The optimal thermal cycle constantly keeps the surface of the part heated and thus creates conditions for obtaining less stressed structures of the recovered part.

The mass saving potential of light-weight materials, such as Al alloys, is beneficial for fuel economy and reducing CO 2 emissions. However, the wide-spread use of these alloys has been long hindered due to the difficulty in fusion joining as well as their high cost. Welding of Al alloys, which are considered to be difficult to weld through conventional arc welding, is now possible by either of low heat input arc welding, high-power density fusion joining, such as laser beam welding and electron beam welding, or friction stir welding. Particularly, friction stir welding can be successfully applied to these materials owing to the fact that no melting takes place in the weld nugget. The aim of this overview is to summarize the developments in the joining of Al alloys over the recent years. This study is also intended to provide guidance for the industry and researchers dealing with joining of these alloys.

Wire arc additive manufacturing (WAAM) is a fusion manufacturing process in which the heat energy of an electric arc is employed for melting the electrodes and depositing material layers for wall formation or for simultaneously cladding two materials in order to form a composite structure. This directed energy deposition-arc (DED-arc) method is advantageous and efficient as it produces large parts with structural integrity due to the high deposition rates, reduced wastage of raw material, and low consumption of energy in comparison with the conventional joining processes and other additive manufacturing technologies. These features have resulted in a constant and continuous increase in interest in this modern manufacturing technique which demands further studies to promote new industrial applications. The high demand for WAAM in aerospace, automobile, nuclear, moulds, and dies industries demonstrates compatibility and reflects comprehensiveness. This paper presents a comprehensive review on the evolution, development, and state of the art of WAAM for non-ferrous materials. Key research observations and inferences from the literature reports regarding the WAAM applications, methods employed, process parameter control, optimization and process limitations, as well as mechanical and metallurgical behavior of materials have been analyzed and synthetically discussed in this paper. Information concerning constraints and enhancements of the wire arc additive manufacturing processes to be considered in terms of wider industrial applicability is also presented in the last part of this paper.

Wire + arc additive manufacturing (WAAM) is a versatile, low-cost, energy-efficient technology used in metal additive manufacturing. This WAAM process uses arc welding to melt a wire and form a three-dimensional (3D) object using a layer-by-layer stacking mechanism. In the present study, a Ni-based superalloy wire, i.e., Inconel 625, is melted and deposited additively through a cold metal transfer (CMT)-based WAAM process. The deposited specimens were heat-treated at 980 °C (the recommended temperature for stress-relief annealing) for 30, 60, and 120 min and then water quenched to investigate the effect of heat treatment on microstructure and phase transformation and to identify the optimum heat treatment condition. Microstructural results show that the heat treatment, in general, eliminates the brittle Laves phases regardless of the time without changing the grain morphology. However, an increment in the amount of the delta phase is observed with the longer heat treatment periods. Additionally, the size of MC (metal carbide) of Nb is also observed to increase with heat treatment time. This study provides an in-depth understanding of the correlation between heat treatment time and microstructure in additively manufactured Inconel 625, which can facilitate determining the optimum heat treatment condition in a later study.

The paper deals with the results of computational and experimental research on the formation process of electric arc discharges in a three-phase Zvezda-type alternating current arc heater. A flow modelling in the arc heater, as well as an experiment on providing a visual control for the location and the shape of arc discharges were conducted. A device of a visual control system is presented. The analysis of the results obtained from experimental research is carried out.

This work aimed at introducing and exploring the potential of a thermal management technique, named as near-immersion active cooling (NIAC), to mitigate heat accumulation in Wire + Arc Additive Manufacturing (WAAM). According to this technique concept, the preform is deposited inside a work tank that is filled with water, whose level rises while the metal layers are deposited. For validation of the NIAC technique, Al5Mg single-pass multi-layer linear walls were deposited by the CMT® process under different thermal management approaches. During depositions, the temperature history of the preforms was measured. Porosity was assessed as a means of analyzing the potential negative effect of the water cooling in the NIAC technique. The preform geometry and mechanical properties were also assessed. The results showed that the NIAC technique was efficient to mitigate heat accumulation in WAAM of aluminum. The temperature of the preforms was kept low independently of its height. There was no measurable increase in porosity with the water cooling. In addition, the wall width was virtually constant, and the anisotropy of mechanical properties tends to be reduced, characterizing a preform quality improvement. Thus, the NIAC technique offers an efficient and low-cost thermal management approach to mitigate heat accumulation in WAAM and, consequently, also to cope with the deleterious issues related to such emerging alternative of additive manufacturing.

A twin-electrode TIG-MIG (T-TIG-MIG) indirect arc welding method was proposed in this paper. The arc behavior and droplet transfer process were preliminarily investigated; moreover, the process stability was assessed, and bead-on-plate welding was conducted. Results showed T-TIG-MIG indirect arc burnt between a wire and two tungsten electrodes and was essentially formed by the coupling of two single-electrode TIG-MIG indirect arcs. The wire feeding speed (WFS) determined the equilibrium position of the wire end, and the vicinity of the tungsten tips was an ideal position for arc shape and droplet detachment, where the arc was more concentrated with a higher coupling degree. With the increase of the welding current, the arc length and stiffness increased gradually; so did the process stability and the spreadability of the weld bead. When the current exceeded the critical current, the droplet transfer mode changed into streaming spray transfer, since the electromagnetic force and the arc pressure increased considerably. Compared to conventional cold-wire T-TIG welding under the same current, the wire deposition rate of T-TIG-MIG indirect arc welding increased by about 186%, while the range of the heat-affected zone reduced by about 41%.