Directed energy deposition (DED) additive manufacturing: Physical characteristics, defects, challenges and applications

Directed energy deposition (DED) is an additive manufacturing technique that employs laser melting to permit for the free form manufacturing of components from many input materials from powder or wire form of feedstock. The nature of DED processes and advancements thereof has led to research that has been aimed at leveraging this additive manufacturing technology for the fabrication of high-value metallic alloys in addition to the exploration of multi-material composites and components – many of which are only possible to produce via DED. Herein, a critical review of the present body of research regarding DED of multi-materials is presented. Assessed are the developing research trends, design methodologies, common issues and challenges, as well as identification of the areas where further research should be directed.

Critical review of the state of the art in multi-material fabrication via directed energy deposition

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

Additive Manufacturing (AM), likewise branded as 3D printing, is a field of significant interest that has been recognized as an advanced process for production of engineering components in a layer-by-layer approach. It both offers an alternative fabrication route for existing designs, as well as enables new designs with complexity unattainable using conventional techniques. Amongst different AM processing routes, Laser Additive Manufacturing (LAM) is one of the supreme encouraging additive manufacturing means due to the potential to fabricate products at low cost with high quality and productivity. Considering many studies are in progress in this new and exciting field, this review paper argues the present state of the art and considers new avenues for future research studies. It explores the key metallurgical phenomena during LAM and the differences between various routes of LAM technology in terms of powder bed fusion (PBF) or directed energy deposition (DED) involving different forms of powder-bed, powder-fed, and wire-fed assembly. The reported microstructural aspects, functional, and mechanical properties of advanced and high applicable materials classified as stainless steels, nickel-based and superalloys, titanium-based alloys, and metal matrix composites (MMCs) for various practical applications are highlighted along with the effects of different pre- and post-treatment characteristics. Hereafter an evaluation of the field is provided; the gaps in the scientific understanding are underlined, which may limit the growth of LAM technology for the design of metallic parts. 

A review on metallurgical aspects of laser additive manufacturing (LAM): Stainless steels, nickel superalloys, and titanium alloys

Abstract Additive Manufacturing (AM) technologies are recognized as the future of the manufacturing industry thanks to their possibilities in terms of shape design, part functionality, and material efficiency. The use of AM technologies in many industrial sectors is growing, also due to the increasing knowledge regarding the AM processes and the characteristics of the final part. One of the most promising AM techniques is the Directed Energy Deposition (DED) that uses a thermal source to generate a melt pool on a substrate into which metal powder is injected. The potentialities of DED technology are the ability to process large build volumes (&gt; 1000 mm in size), the ability to deliver the material directly into the melt pool, the possibility to repair existing parts, and the opportunity to change the material during the building process, thus creating functionally graded material. In this paper, a review of the industrial applications of Laser Powder Directed Energy Deposition (LP-DED) is presented. Three main applications are identified in repairing, designed material, and production. Despite the enormous advantages of LP-DED, from the literature, it emerges that the most relevant application refers to the repairing process of high-value components. 

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Current research and industrial application of laser powder directed energy deposition

Directed energy deposition (DED) is an important additive manufacturing method for producing or repairing high-end and high-value equipment Meanwhile, the lack of reliable and uniform qualities is a key problem in DED applications With the development of sensing devices and control systems, in situ monitoring (IM) and adaptive control (IMAC) technology is an effective method to enhance the reliability and repeatability of DED In this paper, we review current IM technologies in IMAC for metal DED First, this paper describes the important sensing signals and equipment to exhibit the research status in detail Meanwhile, common problems that arise when gathering these signals and resolvent methods are presented Second, process signatures obtained from sensing signals and transfer approaches from sensing signals for processing signatures are shown Third, this work reviews the developments of the IM of product qualities and illustrates ways to realize quality monitoring Lastly, this paper specifies the main existing problems and future research of IM in metal DED

Kaze Mojtaba Saleheen

Papers

A review on in situ monitoring technology for directed energy deposition of metals