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

In this paper, we present a 3D numerical model of Wire Arc Additive Manufacturing to simulate the material deposition and the temperature field from the operating parameters. This predictive model, applied to a Cold Metal Transfer (CMT) process, takes into account electromagnetism, fluid flow and heat transfer in all domains (wire, arc, melt pool, substrate). This model, developed using COMSOL Multiphysics® software, calculates the creation of the molten metal drop at the filler wire tip, the detachment of the drop when the filler material retracts during the short circuiting phase and the growth of the deposit. This innovative work describes for the first time the wire behaviour dynamically and its interaction with the melt pool in 3D in a fully coupled approach. The dynamics of the free surface are treated with the level set method, particularly efficient for strong topological changes. The Lorentz forces, shear stress, arc pressure, and Joule effect are calculated. This model requires only the knowledge of the operating parameters without any assumption on the arc distribution. It aims to simulate the build-up of a 304 stainless steel wall. To validate this model, the melt pool dimensions and shape of the deposit calculated for the first layer are compared to experimental data given by macrographs and high speed videos.

3D heat transfer, fluid flow and electromagnetic model for cold metal transfer wire arc additive manufacturing (Cmt-Waam)

Wire arc additive manufacturing is currently rising as the main focus of research groups around the world. This is directly visible in the huge number of new papers published in recent years concerning a lot of different topics. This review is intended to give a proper summary of the international state of research in the area of wire arc additive manufacturing. The addressed topics in this review include but are not limited to materials (e.g., steels, aluminum, copper and titanium), the processes and methods of WAAM, process surveillance and the path planning and modeling of WAAM. The consolidation of the findings of various authors into a unified picture is a core aspect of this review. Furthermore, it intends to identify areas in which work is missing and how different topics can be synergetically combined. A critical evaluation of the presented research with a focus on commonly known mechanisms in welding research and without a focus on additive manufacturing will complete the review.

The Current State of Research of Wire Arc Additive Manufacturing (WAAM): A Review

Additive manufacturing (AM) route is a promising approach for fabricating complex and lightweight metallic structures that have applications in various sectors such as automotive, aerospace, and biomedical industries. Laser, electron beam, and electric arc are the common power sources available for AM. Out of different metal AM techniques, wire-feed additive manufacturing has been considered as a promising alternative for fabricating metallic parts for various applications. As it provides a high deposition rate, material utilization, density, and low cost with a low risk of contamination and porosity compared to powder-based raw material. Gas metal arc welding-based additive manufacturing (GMAW-AM) is a speciﬁc approach based on wire-feed AM. This technology uses a low-cost equipment which is suitable for fabricating components with large geometries and moderate structural complexity. These advantages attract the researchers and production industries for further developments in GMAW-AM to enhance its deposition performance, process capability, and applicability in various fields. The quality of metal deposited in GMAW-AM is generally represented by the surface form, dimensional quality, mechanical properties, relative density, hardness, etc. The present paper encompasses the research developments that occurred in the field of GMAW-AM in recent years. This review begins with the GMAW-AM procedure, performance capability, identification of factors affecting the deposition performance, and strategies adopted to overcome these issues. Several aspects such as mathematical modelling, optimization, key process parameters, and their combinations for a wide range of wire electrode material and percentage contributions are also reviewed and depicted in detail. Also, a comprehensive conclusion of this review, along with future perspectives, is explored subsequently. The current review work will help future researchers to select different wire materials and GMAW-AM parameters to achieve better performances. Lastly, several future research directions are suggested, specifically the need of a framework for GMAW-AM processes for fabricating quality products with minimum distortion.

Gas metal arc welding based additive manufacturing—a review

Ultra high-frequency pulsed gas tungsten arc welding (UHFP-GTAW)-based Wire Arc Additive Manufacturing (WAAM) was used to fabricate thin walls of NiTi shape memory alloys. The transient heat and fluid flow are critical during fusion-based additive manufacturing, since they impact the as-built microstructure. In this work, a three-dimensional numerical model, which includes the force, surface Gauss heat source and periodic droplet transfer models, was developed to simulate the deposition of 5 layers. The gravity, buoyancy, electromagnetic, surface tension, arc pressure and arc shear stress are considered in the developed force model. An improved free surface tracing method using the volume of fluid (VOF) technique was proposed to more effectively track the free surface of the molten pool with the computational fluid dynamics (CFD) software FLUENT. The multiphysic phenomena associated to the process, namely the temperature and velocity fields of the molten pool, were studied. The model was then validated by experiments. It is revealed that the microstructure of the as-built parts is refined by the UHFP current power which induces significant vibration of the molten pool. These findings lay the foundations for optimizing the WAAM process aiming at fabricating high quality and complex NiTi parts.

S. Cadiou

Papers

3D heat transfer, fluid flow and electromagnetic model for cold metal transfer wire arc additive manufacturing (Cmt-Waam)

Heat transfer, fluid flow and electromagnetic model of droplets generation and melt pool behaviour for wire arc additive manufacturing