Advances in Metal Additive Manufacturing: New Materials, Process Enhancement, Monitoring and Sustainability

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

Deadline for manuscript submissions: closed (30 November 2021) | Viewed by 26076

Special Issue Editors


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Guest Editor
Department of Mechanical Engineering, University of the Basque Country (UPV/EHU), Plaza Ingeniero Torres Quevedo, 48013 Bilbao, Spain
Interests: laser material processing; metal additive manufacturing; laser material deposition; laser process modeling; environmental impact
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Guest Editor
Department of Mechanical Engineering, Faculty of Engineering, University of the Basque Country (UPV/EHU), Plaza Torres Quevedo 1, 48013 Bilbao, Bizkaia, Spain
Interests: laser material processing; metal additive manufacturing; laser material deposition; laser process simulation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Additive manufacturing (AM) is a technology that is gaining relevance in both academia and industry. One of the main fields within AM technology is metal additive manufacturing (MAM), which is expected to be a disruptive technology capable of changing the current production situation. Nevertheless, the technology readiness of MAM is far from its full industrialization, and there is still a great gap between commercial solutions and industry requirements in terms of cost, productivity, and process reliability. Therefore, research efforts are still required to achieve the required maturity of this technology.

In view of this need, some companies, research centers, and universities have begun to investigate in this field. Hence, in the present Special Issue, the editors aim to collect and disseminate the latest developments in MAM. Special attention will be given to the following topics, although the Special Issue is not limited to them:

  • Development of new materials for metal additive manufacturing;
  • Process monitoring for increase the reliability of MAM processes;
  • MAM process enhancement based on closed-loop control and online monitoring systems;
  • Numerical and analytical models focused on at metal additive manufacturing;
  • Post-processing of the additively manufactured parts, where both machinability of the deposited materials as well as the heat treatments are included, among others;
  • Studies related with the environmental impact of metal additive manufacturing, health and safety, waste management, energy consumption, etc.
Dr. Jon Iñaki Iñaki Arrizubieta
Prof. Dr. Aitzol Lamíkiz
Guest Editors

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Keywords

  • metal additive manufacturing
  • monitoring
  • control
  • enhancement
  • modeling
  • environmental impact
  • materials

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Published Papers (5 papers)

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Research

22 pages, 31962 KiB  
Article
Hot-Wire Laser-Directed Energy Deposition: Process Characteristics and Benefits of Resistive Pre-Heating of the Feedstock Wire
by Agnieszka Kisielewicz, Karthikeyan Thalavai Pandian, Daniel Sthen, Petter Hagqvist, Maria Asuncion Valiente Bermejo, Fredrik Sikström and Antonio Ancona
Metals 2021, 11(4), 634; https://doi.org/10.3390/met11040634 - 13 Apr 2021
Cited by 27 | Viewed by 4808
Abstract
This study investigates the influence of resistive pre-heating of the feedstock wire (here called hot-wire) on the stability of laser-directed energy deposition of Duplex stainless steel. Data acquired online during depositions as well as metallographic investigations revealed the process characteristic and its stability [...] Read more.
This study investigates the influence of resistive pre-heating of the feedstock wire (here called hot-wire) on the stability of laser-directed energy deposition of Duplex stainless steel. Data acquired online during depositions as well as metallographic investigations revealed the process characteristic and its stability window. The online data, such as electrical signals in the pre-heating circuit and images captured from side-view of the process interaction zone gave insight on the metal transfer between the molten wire and the melt pool. The results show that the characteristics of the process, like laser-wire and wire-melt pool interaction, vary depending on the level of the wire pre-heating. In addition, application of two independent energy sources, laser beam and electrical power, allows fine-tuning of the heat input and increases penetration depth, with little influence on the height and width of the beads. This allows for better process stability as well as elimination of lack of fusion defects. Electrical signals measured in the hot-wire circuit indicate the process stability such that the resistive pre-heating can be used for in-process monitoring. The conclusion is that the resistive pre-heating gives additional means for controlling the stability and the heat input of the laser-directed energy deposition. Full article
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14 pages, 4428 KiB  
Article
Laser Powder Bed Fusion (PBF-LB/M) Process Strategies for In-Situ Alloy Formation with High-Melting Elements
by Florian Huber, Michael Rasch and Michael Schmidt
Metals 2021, 11(2), 336; https://doi.org/10.3390/met11020336 - 16 Feb 2021
Cited by 17 | Viewed by 6924
Abstract
In-situ alloy formation by Laser Powder Bed Fusion (PBF-LB/M) from mixtures of easily available elemental powders is an appealing approach for developing and qualifying new alloys for laser based additive manufacturing of metals. However, especially when dealing with high-melting elements, like W, Ta, [...] Read more.
In-situ alloy formation by Laser Powder Bed Fusion (PBF-LB/M) from mixtures of easily available elemental powders is an appealing approach for developing and qualifying new alloys for laser based additive manufacturing of metals. However, especially when dealing with high-melting elements, like W, Ta, Mo, or Nb, it is difficult to achieve a homogeneous element distribution and a complete fusion of the powder particles. The aim of this work was to understand the effects of the PBF-LB/M process parameters (laser power, scan speed, laser spot diameter) and three different single- and double-exposure strategies on the fusion of high-melting W, Ta, Mo, and Nb particles in a Ti-matrix. For this purpose, 220 samples with 10 vol.% of the high-melting particle fraction were prepared and analyzed by optical light microscopy and automated image processing, as well as by scanning electron microscopy (SEM). The results are discussed in the context of current research on the process dynamics of PBF-LB/M. Based on that process strategies to support a complete fusion of high-melting particles during in-situ alloy formation are derived. It is shown that the number of unmolten particles can be at least decreased by a factor of ten compared to the most unfavorable parameter combination. For the lower melting elements, Nb and Mo, a complete fusion without any remaining particles visible in the microsections was achieved for certain parameter combinations. The results prove the feasibility of in-situ alloy formation with high-melting alloying elements, but they also demonstrate the necessity to adjust the PBF-LB/M process strategy to achieve a complete dissolution of the alloying elements. Full article
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18 pages, 39936 KiB  
Article
Strategy Development for the Manufacturing of Multilayered Structures of Variable Thickness of Ni-Based Alloy 718 by Powder-Fed Directed Energy Deposition
by Pedro Ramiro, Mikel Ortiz, Amaia Alberdi and Aitzol Lamikiz
Metals 2020, 10(10), 1280; https://doi.org/10.3390/met10101280 - 24 Sep 2020
Cited by 10 | Viewed by 3980
Abstract
In this study, a manufacturing strategy, and guidelines for inclined and multilayered structures of variable thickness are presented, which are based on the results of an own-developed geometrical model that obtains both the coating thickness and dilution. This model is developed for the [...] Read more.
In this study, a manufacturing strategy, and guidelines for inclined and multilayered structures of variable thickness are presented, which are based on the results of an own-developed geometrical model that obtains both the coating thickness and dilution. This model is developed for the powder-fed directed energy deposition process (DED) and it only uses the DED single-track cladding characteristics (height, width, area, and dilution depth), the overlap percentage, and the laser head tilting-angle as inputs. As outputs, it calculates both the cladding geometry and the dilution area of the coating. This model for the Ni-based alloy 718 was improved, based on previous studies of the single clad working both vertically and at an inclined angle, adding the equations of the single clad characteristics with respect to the main process parameters. The strategy proposed in this paper for multilayered cladding consisted of both adding an extra clad at the edges of the layer and using a variable value of the overlap percentage between clads for geometric adaptations. With this strategy, the material deposition is more accurate than otherwise, and it shows stable growth. Manufacturing a multilayered wall of wider thicknesses at higher heights was utilized to validate the strategy. Full article
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19 pages, 7523 KiB  
Article
Analysis of the Wall Geometry with Different Strategies for High Deposition Wire Arc Additive Manufacturing of Mild Steel
by Eider Aldalur, Fernando Veiga, Alfredo Suárez, Jon Bilbao and Aitzol Lamikiz
Metals 2020, 10(7), 892; https://doi.org/10.3390/met10070892 - 4 Jul 2020
Cited by 46 | Viewed by 5619
Abstract
Additive manufacturing has gained relevance in recent decades as an alternative to the manufacture of metal parts. Among the additive technologies, those that are classified as Directed Energy Deposition (DED) are characterized by their high deposition rate, noticeably, Wire Arc Additive Manufacturing (WAAM). [...] Read more.
Additive manufacturing has gained relevance in recent decades as an alternative to the manufacture of metal parts. Among the additive technologies, those that are classified as Directed Energy Deposition (DED) are characterized by their high deposition rate, noticeably, Wire Arc Additive Manufacturing (WAAM). However, having the inability to produce parts with acceptable final surface quality and high geometric precision is to be considered an important disadvantage in this process. In this paper, different torch trajectory strategies (oscillatory motion and overlap) in the fabrication of low carbon steel walls will be compared using Gas Metal Arc Welding (GMAW)-based WAAM technology. The comparison is done with a study of the mechanical and microstructural characteristics of the produced walls and finally, addressing the productivity obtained utilizing each strategy. The oscillation strategy shows better results, regarding the utilization rate of deposited material and the flatness of the upper surface, this being advantageous for subsequent machining steps. Full article
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10 pages, 3427 KiB  
Article
Effect of Hot Isostatic Pressing on Microstructures and Mechanical Properties of Ti6Al4V Fabricated by Electron Beam Melting
by Changyong Liu, Zhuokeng Mai, Deng Yan, Mingguang Jiang, Yuhong Dai, Pei Wang, Zhangwei Chen and Changshi Lao
Metals 2020, 10(5), 593; https://doi.org/10.3390/met10050593 - 30 Apr 2020
Cited by 9 | Viewed by 3637
Abstract
This study investigated the effects of hot isostatic pressing (HIP) on the microstructures and mechanical properties of Ti6Al4V fabricated by electron beam melting (EBM). The differences of surface morphologies, internal defects, relative density, microstructures, textures, mechanical properties and tensile fracture between the as-built [...] Read more.
This study investigated the effects of hot isostatic pressing (HIP) on the microstructures and mechanical properties of Ti6Al4V fabricated by electron beam melting (EBM). The differences of surface morphologies, internal defects, relative density, microstructures, textures, mechanical properties and tensile fracture between the as-built and HIPed samples were observed using various characterization methods including optical metallography microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) and tensile tests. It was found that the main effects of HIP on microstructures include—the increase of average grain size from 7.96 ± 1.21 μm to 11.34 ± 1.89 μm, the increase of α lamellar thickness from 0.71 ± 0.15 μm to 2.49 ± 1.29 μm and the increase of β phase ratio from 4.7% to 10.5% in terms of area fraction on the transversal section. The combinatorial effects including densification, increase of grain size, α lamellar thickness, β phase ratio, reduction of dislocation density and transformation of dislocation patterns contributed to the improvement of elongation and ductility of EBM-fabricated Ti6Al4V. Meanwhile, these effects also resulted in a slight reduction of the yield strength and UTS mainly due to the coarsening effect of HIP. Full article
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