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Directed Energy Deposition of Metal Alloys

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Additive Manufacturing".

Deadline for manuscript submissions: closed (31 January 2023) | Viewed by 38829

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Prof. Dr. Joel Andersson

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Department of Engineering Science, University West, Trollhättan, Sweden
Interests: additive manufacturing; welding and weldability testing; materials engineering and materials physics
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Special Issue Information

Dear Colleagues,

Directed Energy Deposition enhances material utilization by enabling the manufacture of high-precision near-net shape components from wire and powders. The main advantages of wire as a feedstock compared to powder is a higher deposition rate, fewer porosities in the deposited material, as well as better surface finish. However, this comes at the cost of higher heat input. Additionally, there is an inherent challenge in wire deposition when it comes to controlling the process. Historically, metal deposition technologies have been of most interest in high value-added applications such as in aerospace, space, and medicine which can afford this developing process, despite the tough performance and acceptance criteria in these industrial sectors. Components can be repaired, remanufactured, or semi-finished components can be used to add features to by metal deposition, but care must be taken regarding heat input to avoid impairment of material strength and distortion. Anisotropy in the mechanical properties is a concern due to the layered microstructure as well as the residual stresses that are commonly present because of steep thermal gradients. The metal deposition parts have very complex thermal histories, which depend on process variables. The influence of process parameters on the microstructure is complex with a strong dependence on the material system. A current concern with metal deposition is that it is very hard to predict the properties of these components since there are so many process variables involved in the process. This Special Issue on metal deposition technologies intends to offer a dedicated platform for sharing new findings, communicating views about the accomplishments, and future directions in metal deposition research. We welcome reviews and original research articles in the areas of metallurgy, process monitoring, and control, as well as associated topics of metal deposition, achieved through either experimental techniques or theoretical calculations.

Dr. Joel Andersson
Guest Editor

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Keywords

directed energy deposition
wire arc additive manufacturing
production
repair
remanufacturing
cladding
wire
powder

Published Papers (10 papers)

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Editorial

Jump to: Research, Review

6 pages, 191 KiB

Open AccessEditorial

Directed Energy Deposition of Metal Alloys

by Joel Andersson

Metals 2024, 14(5), 537; https://doi.org/10.3390/met14050537 - 1 May 2024

Viewed by 1080

Abstract

Directed energy deposition (DED) stands as an advancement in material utilization, facilitating the production of highly precise near-net shape components using wire and powders [...] Full article

(This article belongs to the Special Issue Directed Energy Deposition of Metal Alloys)

Research

Jump to: Editorial, Review

20 pages, 7653 KiB

Open AccessArticle

Proposal and Assessment of a Multiple Cycle-Continuous Cooling Transformation (MC-CCT) Diagram for Wire Arc Additive Manufacturing of Thin Walls

by Mats Högström, Amirhosein Fadaei, Amin Rahimi, Peigang Li, Mattias Igestrand, Joel Andersson and Americo Scotti

Metals 2023, 13(9), 1533; https://doi.org/10.3390/met13091533 - 29 Aug 2023

Cited by 1 | Viewed by 1687

Abstract

Continuous cooling transformation (CCT) diagrams of base metals are common in welding. They can be built using physical or numerical simulations, each with advantages and limitations. However, those are not usual for weld metal, considering its variable composition due to the dilution of the weld into the base metal. Wire Arc Additive Manufacturing (WAAM) is a distinctive case in which the interest in materials comparable with weld composition raises attention to estimating their mechanical properties. Notwithstanding, this concept is still not used in WAAM. Therefore, the aim of this work was to address a methodology to raise MC-CCT (Multiple Cycle Continuous Cooling Transformation) diagrams for WAAM by combining physical and numerical simulations. A high-strength low-alloy steel (HSLA) feedstock (a combination of a wire and a shielding gas) was used as a case study. To keep CCT as representative as possible, the typical multiple thermal cycles for additive manufacturing thin walls were determined and replicated in physical simulations (Gleeble dilatometry). The start and end transformations were determined by the differential linear variation approach for each thermal cycle. Microstructure analyses and hardness were used to characterise the product after the multiple cycles. The same CCT diagram was raised by a commercial numerical simulation package to determine the shape of the transformation curves. A range of austenitic grain sizes was scanned for the curve position matching the experimental results. Combining the experimental data and numerically simulated curves made estimating the final CCT diagram possible. Full article

(This article belongs to the Special Issue Directed Energy Deposition of Metal Alloys)

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18 pages, 10303 KiB

Open AccessArticle

Effect of Heat Treatment on the Microstructure and Hardness of Ni-Based Alloy 718 in a Variable Thickness Geometry Deposited by Powder Fed Directed Energy Deposition

by Pedro Ramiro, Haize Galarraga, Anabel Pérez-Checa, Mikel Ortiz, Amaia Alberdi, Trunal Bhujangrao, Elena Morales and Eneko Ukar

Metals 2022, 12(6), 952; https://doi.org/10.3390/met12060952 - 31 May 2022

Cited by 3 | Viewed by 2586

Abstract

Feature addition to existing parts is a trending application for Directed Energy Deposition (DED) and can be used to add complex geometry features to basic forged geometries with the aim to reduce and simplify the number of processing steps as machining and assembling. However, the mechanical properties of as-deposited Inconel 718 fabricated by Powder-fed Directed Energy Deposition (Powder-fed DED) are far lower than the relevant specifications, making it necessary to apply different heat treatment with the purpose of improving deposited material performance. In addition, the effects of heat treatments in both variable thickness deposited geometry and forge substrate have not been studied. In this study, the effect of heat treatment within the Aerospace Materials Specifications (AMS) for cast and wrought Inconel 718 on the microstructure and hardness of both the Ni-Based Alloy 718 deposited geometry and substrate are analyzed in different parts of the geometry. The microstructure of all samples (as-deposited and heat-treated) is analyzed by Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS), confirming the formation of aluminum oxides and titanium nitrides and carbonitrides in the deposited structure. Full article

(This article belongs to the Special Issue Directed Energy Deposition of Metal Alloys)

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19 pages, 9193 KiB

Open AccessFeature PaperArticle

In-Situ Laser Directed Energy Deposition of Biomedical Ti-Nb and Ti-Zr-Nb Alloys from Elemental Powders

by Felipe Arias-González, Alejandra Rodríguez-Contreras, Miquel Punset, José María Manero, Óscar Barro, Mónica Fernández-Arias, Fernando Lusquiños, Francisco Javier Gil and Juan Pou

Metals 2021, 11(8), 1205; https://doi.org/10.3390/met11081205 - 28 Jul 2021

Cited by 17 | Viewed by 3143

Abstract

In order to achieve the required properties of titanium implants, more resources and research are needed to turn into reality the dream of developing the perfect implant material. The objective of this study was to evaluate the viability of the Laser Directed Energy Deposition to produce biomedical Ti-Nb and Ti-Zr-Nb alloys from elemental powders (Ti, Nb and Zr). The Laser Directed Energy Deposition is an additive manufacturing process used to build a component by delivering energy and material simultaneously. The material is supplied in the form of particles or wire and a laser beam is employed to melt material that is selectively deposited on a specified surface, where it solidifies. Samples with different compositions are characterized to analyze their morphology, microstructure, constituent phases, mechanical properties, corrosion resistance and cytocompatibility. Laser-deposited Ti-Nb and Ti-Zr-Nb alloys show no relevant defects, such as pores or cracks. Titanium alloys with lower elastic modulus and a significantly higher hardness than Ti grade 2 were generated, therefore a better wear resistance could be expected from them. Moreover, their corrosion resistance is excellent due to the formation of a stable passive protective oxide film on the surface of the material; in addition, they also possess outstanding cytocompatibility. Full article

(This article belongs to the Special Issue Directed Energy Deposition of Metal Alloys)

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12 pages, 3661 KiB

Open AccessArticle

Directed Energy Deposition of AISI 316L Stainless Steel Powder: Effect of Process Parameters

by Alberta Aversa, Giulio Marchese and Emilio Bassini

Metals 2021, 11(6), 932; https://doi.org/10.3390/met11060932 - 8 Jun 2021

Cited by 30 | Viewed by 5284

Abstract

During Laser Powder-Directed Energy Deposition (LP-DED), many complex phenomena occur. These phenomena, which are strictly related to the conditions used during the building process, can affect the quality of the parts in terms of microstructural features and mechanical behavior. This paper investigates the effect of building parameters on the microstructure and the tensile properties of AISI 316L stainless-steel samples produced via LP-DED. Firstly, the building parameters were selected starting from single scan tracks by studying their morphology and geometrical features. Next, 316L LP-DED bulk samples built with two sets of parameters were characterized in terms of porosity, geometrical accuracy, microstructure, and mechanical properties. The tensile tests data were analyzed using the Voce model and a correlation between the tensile properties and the dislocation free path was found. Overall, the data indicate that porosity should not be considered the unique indicator of the quality of an LP-DED part and that a mechanical characterization should also be performed. Full article

(This article belongs to the Special Issue Directed Energy Deposition of Metal Alloys)

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15 pages, 46039 KiB

Open AccessFeature PaperArticle

Effect of Substrate Alloy Type on the Microstructure of the Substrate and Deposited Material Interface in Aluminium Wire + Arc Additive Manufacturing

by Eloise Eimer, Stewart Williams, Jialuo Ding, Supriyo Ganguly and Bechir Chehab

Metals 2021, 11(6), 916; https://doi.org/10.3390/met11060916 - 4 Jun 2021

Cited by 9 | Viewed by 3673

Abstract

Wire + Arc Additive Manufacture is an Additive Manufacturing process that requires a substrate to initiate the deposition process. In order to reduce material waste, build and lead time, and improve process efficiency, it is desirable to include this substrate in the final part design. This approach is a valid option only if the interface between the substrate and the deposited metal properties conform to the design specifications. The effect of substrate type on the interface microstructure in an aluminium part was investigated. Microstructure and micro-hardness measurements show the effect of substrate alloy and temper on the interface between the substrate and deposited material. Microcracks in the as-deposited condition were only found in one substrate. The deposited material hardness is always lower than the substrate hardness. However, this difference can be minimised by heat treatment and even eliminated when the substrate and wire are made of the same alloy. Full article

(This article belongs to the Special Issue Directed Energy Deposition of Metal Alloys)

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18 pages, 6668 KiB

Open AccessFeature PaperArticle

Strategies to Reduce Porosity in Al-Mg WAAM Parts and Their Impact on Mechanical Properties

by Maider Arana, Eneko Ukar, Iker Rodriguez, Amaia Iturrioz and Pedro Alvarez

Metals 2021, 11(3), 524; https://doi.org/10.3390/met11030524 - 23 Mar 2021

Cited by 27 | Viewed by 4517

Abstract

With the advent of disruptive additive manufacturing (AM), there is an increasing interest and demand of high mechanical property aluminium parts built directly by these technologies. This has led to the need for continuous improvement of AM technologies and processes to obtain the best properties in aluminium samples and develop new alloys. This study has demonstrated that porosity can be reduced below 0.035% in area in Al-Mg samples manufactured by CMT-based WAAM with commercial filler metal wires by selecting the correct shielding gas, gas flow rate, and deposition strategy (hatching or circling). Three phase Ar+O₂+N₂O mixtures (Stargold^®) are favourable when the hatching deposition strategy is applied leading to wall thickness around 6 mm. The application of circling strategy (torch movement with overlapped circles along the welding direction) enables the even build-up of layers with slightly thicker thickness (8 mm). In this case, Ar shielding gas can effectively reduce porosity if proper flow is provided through the torch. Reduced gas flows (lower than 30 Lmin) enhance porosity, especially in long tracks (longer than 90 mm) due to local heat accumulation. Surprisingly, rather high porosity levels (up to 2.86 area %) obtained in the worst conditions, had a reduced impact on the static tensile test mechanical properties, and yield stress over 110 MPa, tensile strength over 270 MPa, and elongation larger than 27% were achieved either for Ar circling, Ar hatching, or Stargold^® hatching building conditions. In all cases anisotropy was lower than 11%, and this was reduced to 9% for the most appropriate shielding conditions. Current results show that due to the selected layer height and deposition parameters there was a complete re-melting of the previous layer and a thermal treatment on the prior bottom layer that refined the grain size removing the original dendritic and elongated structure. Under these conditions, the minimum reported anisotropy levels can be achieved. Full article

(This article belongs to the Special Issue Directed Energy Deposition of Metal Alloys)

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20 pages, 7586 KiB

Open AccessFeature PaperArticle

The Concept of a Novel Path Planning Strategy for Wire + Arc Additive Manufacturing of Bulky Parts: Pixel

by Rafael Pereira Ferreira and Américo Scotti

Metals 2021, 11(3), 498; https://doi.org/10.3390/met11030498 - 17 Mar 2021

Cited by 12 | Viewed by 3712

Abstract

An innovative trajectory strategy was proposed and accessed for wire arc additive manufacturing (WAAM), applicable to different and more complex geometries, rather than being a single solution. This strategy, named Pixel, can be defined as a complex multitask procedure to carry out optimized path planning, whose operation is made through computational algorithms (heuristics), with accessible computational resources and tolerable computational time. The model layers are fractioned in squared grids, and a set of dots is systematically generated and distributed inside the sliced outlines, resembling pixels on a screen, over which the trajectory is planned. The Pixel strategy was based on creating trajectories from the technique travelling salesman problem (TSP). Unlike existing algorithms, the Pixel strategy uses an adapted greedy randomized adaptive search procedure (GRASP) metaheuristic, aided by four concurrent trajectory planning heuristics, developed by the authors. Interactions provide successive trajectories from randomized initial solutions (global search) and subsequent iterative improvements (local search). After all recurrent loops, a trajectory is defined and written in machine code. Computational evaluation was implemented to demonstrate the effect of each of the heuristics on the final trajectory. An experimental evaluation was eventually carried out using two different not easily printable shapes to demonstrate the practical feasibility of the proposed strategy. Full article

(This article belongs to the Special Issue Directed Energy Deposition of Metal Alloys)

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16 pages, 4960 KiB

Open AccessArticle

Effect of Direct Energy Deposition Process Parameters on Single-Track Deposits of Alloy 718

by Suhas Sreekanth, Ehsan Ghassemali, Kjell Hurtig, Shrikant Joshi and Joel Andersson

Metals 2020, 10(1), 96; https://doi.org/10.3390/met10010096 - 7 Jan 2020

Cited by 43 | Viewed by 7202

Abstract

The effect of three important process parameters, namely laser power, scanning speed and laser stand-off distance on the deposit geometry, microstructure and segregation characteristics in direct energy deposited alloy 718 specimens has been studied. Laser power and laser stand-off distance were found to notably affect the width and depth of the deposit, while the scanning speed influenced the deposit height. An increase in specific energy conditions (between 0.5 J/mm² and 1.0 J/mm²) increased the total area of deposit yielding varied grain morphologies and precipitation behaviors which were comprehensively analyzed. A deposit comprising three distinct zones, namely the top, middle and bottom regions, categorized based on the distinct microstructural features formed on account of variation in local solidification conditions. Nb-rich eutectics preferentially segregated in the top region of the deposit (5.4–9.6% area fraction, A_f) which predominantly consisted of an equiaxed grain structure, as compared to the middle (1.5–5.7% A_f) and the bottom regions (2.6–4.5% A_f), where columnar dendritic morphology was observed. High scan speed was more effective in reducing the area fraction of Nb-rich phases in the top and middle regions of the deposit. The <100> crystallographic direction was observed to be the preferred growth direction of columnar grains while equiaxed grains had a random orientation. Full article

(This article belongs to the Special Issue Directed Energy Deposition of Metal Alloys)

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Review

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18 pages, 4755 KiB

Open AccessReview

Preventing Evaporation Products for High-Quality Metal Film in Directed Energy Deposition: A Review

by Kang-Hyung Kim, Chan-Hyun Jung, Dae-Yong Jeong and Soong-Keun Hyun

Metals 2021, 11(2), 353; https://doi.org/10.3390/met11020353 - 19 Feb 2021

Cited by 4 | Viewed by 3328

Abstract

Directed energy deposition (DED), a type of additive manufacturing (AM) is a process that enables high-speed deposition using laser technology. The application of DED extends not only to 3D printing, but also to the 2D surface modification by direct laser-deposition dissimilar materials with a sub-millimeter thickness. One of the reasons why DED has not been widely applied in the industry is the low velocity with a few m/min, but thin-DED has been developed to the extent that it can be over 100 m/min in roller deposition. The remaining task is to improve quality by reducing defects. Thus far, defect studies on AM, including DED, have focused mostly on preventing pores and crack defects that reduce fatigue strength. However, evaporation products, fumes, and spatters, were often neglected despite being one of the main causes of porosity and defects. In high-quality metal deposition, the problems caused by evaporation products are difficult to solve, but they have not yet caught the attention of metallurgists and physicists. This review examines the effect of the laser, material, and process parameters on the evaporation products to help obtain a high-quality metal film layer in thin-DED. Full article

(This article belongs to the Special Issue Directed Energy Deposition of Metal Alloys)

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