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Metal Additive Manufacturing and Its Post Processing Techniques

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A special issue of Journal of Manufacturing and Materials Processing (ISSN 2504-4494).

Deadline for manuscript submissions: closed (30 September 2022) | Viewed by 51375

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Special Issue Editors

Dr. Hao Wang

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Guest Editor

Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore
Interests: hybrid and additive manufacturing; post-processing; ultraprecision machining
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Jerry Fuh

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Guest Editor

NUS Centre for Additive Manufacturing (AM.NUS) and Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore
Interests: additive manufacturing; bioprinting; metal/ceramic 3D printing; AM for biomedical applications

Special Issue Information

Additive manufacturing (AM) has been attracting tremendous attention in recent decades due to its unique advantages over conventional subtractive manufacturing processes in terms of customization and complex geometry and near-net-shape fabrication. To date, the application of AM technology has been extended to various fields of engineering, including automobile, aerospace, medical, and biomedical industries. Although the development of AM technology has been relatively successful at attaining sufficient mechanical properties, actual component adoption in the industry is still limited by the achievable surface finish and geometric accuracy. In this regard, post-processing is essential to remove support structures, tune microstructure and material properties, correct form errors, and improve surface finish. Post-processing methods commonly employ conventional subtractive manufacturing techniques that have been well established for shaping and finishing. It is desirable and challenging to integrate conventional manufacturing processes with the unique features of the additively manufactured components. The aim of this Special Issue is to provide the researchers and practitioners from academia and industries a forum for reviewing and discussing the state-of-the-art developments and future directions in the area of metal additive manufacturing and its hybrid post-processing technologies. For this Special Issue “Metal Additive Manufacturing and Its Post Processing Techniques” we invite papers that introduce the most innovative advances and enlighten on the scientific understanding of metal additive manufacturing technologies and post-processing methods through theoretical and/or experimental aspects of one or more of the following example topic areas:

New processes and applications of metal additive manufacturing
Material characterization and modelling for metal additive manufacturing
Machine tools and processes for hybrid additive and subtractive manufacturing
3D printing for large-format components for industry applications
AI technologies in metal additive manufacturing
Non-conventional post-processing methods and applications
Mechanical, abrasive, chemical, and electrochemical post-processing for AM
Robot-assisted additive manufacturing and its post-processing
Development of post-processing equipment/device for additive manufacturing

Dr. Hao Wang
Prof. Dr. Jerry Fuh
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Journal of Manufacturing and Materials Processing is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

additive manufacturing
3D printing
post-processing
hybrid manufacturing
microstructure
material characterization
geometric accuracy
modelling and simulation

Published Papers (11 papers)

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Editorial

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2 pages, 185 KiB

Open AccessEditorial

Metal Additive Manufacturing and Its Post-Processing Techniques

by Hao Wang and Jerry Ying Hsi Fuh

J. Manuf. Mater. Process. 2023, 7(1), 47; https://doi.org/10.3390/jmmp7010047 - 10 Feb 2023

Cited by 2 | Viewed by 2298

Abstract

Metal additive manufacturing has made substantial progress in the advanced manufacturing sector with competitive advantages for the efficient production of high-quality products [...] Full article

(This article belongs to the Special Issue Metal Additive Manufacturing and Its Post Processing Techniques)

Research

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18 pages, 8182 KiB

Open AccessArticle

Comprehensive and Comparative Heat Treatment of Additively Manufactured Inconel 625 Alloy and Corresponding Microstructures and Mechanical Properties

by Victoria Luna, Leslie Trujillo, Ariel Gamon, Edel Arrieta, Lawrence E. Murr, Ryan B. Wicker, Colton Katsarelis, Paul R. Gradl and Francisco Medina

J. Manuf. Mater. Process. 2022, 6(5), 107; https://doi.org/10.3390/jmmp6050107 - 26 Sep 2022

Cited by 7 | Viewed by 2689

Abstract

This study examines and compares the microstructures, Vickers microindentation hardness, and mechanical properties for additively manufactured (AM) samples built by a variety of AM processes: wire arc AM (WAAM), electron beam powder bed fusion (EB-PBF), laser wire direct energy deposition (LW-DED), electron beam direct energy deposition (EB-DED), laser-powered direct energy deposition (LP-DED), and laser powder bed fusion (L-PBF). These AM process samples were post-processed and heat-treated by stress relief annealing at 1066 °C, HIP at 1163 °C, and solution annealing treatment at 1177 °C. The resulting microstructures and corresponding microindentation hardnesses were examined and compared with the as-built AM process microstructures and hardnesses. Fully heat-treated AM process samples were mechanically tested to obtain tensile properties and were also evaluated and compared. Principal findings in this study were that high-temperature heat treatment >1100 °C of AM process-built samples was dominant and exhibited recrystallized, equiaxed grains containing fcc {111} annealing twins and second phase particles independent of the AM process, in contrast to as-built columnar/dendritic structures. The corresponding yield stress values ranged from 285 MPa to 371 MPa, and elongations ranged from 52% to 70%, respectively. Vickers microindentation hardnesses (HV) over this range of heat-treated samples varied from HV 190 to HV 220, in contrast to the as-built samples, which varied from HV 191 to HV 304. Full article

(This article belongs to the Special Issue Metal Additive Manufacturing and Its Post Processing Techniques)

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17 pages, 4444 KiB

Open AccessArticle

Influences of Surface, Heat Treatment, and Print Orientation on the Anisotropy of the Mechanical Properties and the Impact Strength of Ti 6Al 4V Processed by Laser Powder Bed Fusion

by Benjamin Meier, Norica Godja, Fernando Warchomicka, Carlos Belei, Sandra Schäfer, Andreas Schindel, Gregor Palcynski, Reinhard Kaindl, Wolfgang Waldhauser and Christof Sommitsch

J. Manuf. Mater. Process. 2022, 6(4), 87; https://doi.org/10.3390/jmmp6040087 - 14 Aug 2022

Cited by 8 | Viewed by 2605

Abstract

The scope of this work is to provide an overview of the influences of process parameters, print orientation, and post-process treatments of Ti6AlV4 processed by laser powder bed fusion on its microstructure and physical and mechanical properties and their anisotropic behavior. To avoid the influence of changes in powder quality and ensure comparability, experiments were carried out using a single batch of virgin powder. First, characterization of the density and surface roughness was performed to optimize the process parameters utilizing design of experiment. Tensile, notched bar impact and compression test specimens were built in three different orientations: vertically, horizontally, and inclined at 45° to the build plate. Later, the influence of the staircase effect and the possible course of anisotropy from vertical to horizontal were investigated. Subsequently, heat treatments for stress relief, furnace annealing, and hot isostatic pressing were performed. In addition to as-built samples, mechanical machining and a two-step electrochemical polishing surface treatment were applied to investigate the influence of the surface roughness. With parameter optimization, a relative density of 99.8% was achieved, and surface roughness was improved over default parameters, reducing Ra by up to 7 µm. Electrochemical polishing is a viable way to decrease the surface roughness. An Ra value of 1 µm and an Rz value of 4 µm can be achieved for 45° downskin surfaces with as-built surface roughness values of Ra 24 µm and Rz 117 µm. As-built and stress-relieved conditions show little anisotropy in their yield and tensile strength (max 2.7%), but there is a strong influence of the build orientation on necking, and brittle fracture behavior is shown due to the martensitic microstructure (up to 70%). Heat treatment can increase the ductility and further decrease the strength anisotropy with both furnace annealing and hot isostatic pressing delivering similar results for tensile properties, while angled samples exhibit behavior that is closer to vertical than horizontal, indicating a non-linear change in break behavior. Electrochemical polishing increases fracture necking, and its isotropy drastically increases from 4% to over 30% compared with as-built parts, which is close to the level of the machined specimen. Full article

(This article belongs to the Special Issue Metal Additive Manufacturing and Its Post Processing Techniques)

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23 pages, 57720 KiB

Open AccessFeature PaperArticle

Influence of Post-Processing Conditions on the Microstructure, Static, and Fatigue Resistance of Laser Powder Bed Fused Ti-6Al-4V Components

by Erika Herrera Jimenez, Alena Kreitcberg, Etienne Moquin and Vladimir Brailovski

J. Manuf. Mater. Process. 2022, 6(4), 85; https://doi.org/10.3390/jmmp6040085 - 08 Aug 2022

Cited by 7 | Viewed by 2715

Abstract

The microstructure, static, and fatigue mechanical properties of laser powder bed fused (LPBF) Ti-6Al-4V components subjected to three different post-processing treatments (PTs) are compared. The first treatment includes stress relief (SR) and beta-phase annealing (BA) heat treatments, the second one includes SR, beta-solution (BST) and over aging (OA) heat treatments, and the third procedure is a combination of hot isostatic pressing (HIP) and BST + OA. It was demonstrated that the three PTs led to the decomposition of α’ martensite inherited from the LPBF process and the formation of variable α + β structures. The SR + BA treatment forms a basket weave structure having an average α lamellae width of ~3 µm and surrounded by ~1 µm-sized zones of segregated β phase (4.6–5.2% β phase content) and globalized α phase (~10 µm in size) inside prior columnar β grains (~100 µm in width). The SR + BST + OA treatment forms semi-equiaxed α grains (~300 µm) containing colonies (~50 µm) of parallel-oriented α plates (~6 µm), and β phase (5.8–7.5%) in the interplate spacing. The HIP + BST + OA treatment leads to the formation of large grains (~500 µm) with both basket weave and colony (~40 µm) α structures containing α plates (1.1–4.2 µm) and β phase (5–7.1%). To compare the impact of these PTs on the mechanical properties of LPBF components, they were subjected to static and fatigue tensile testing at room temperature. The best combination of mechanical properties (yield strength ~920 MPa, ultimate strength ~1000 MPa, elongation to break ~22.5%, and fatigue strength ~600 MPa, 10⁷ cycles) was obtained in the case of SR + BA specimens. These results demonstrate that an adequate thermal treatment, such as SR + BA, of the LPBF Ti64 components, could be a valuable and less expensive alternative to the established HIP + BST + OA treatment procedure when fatigue life is the main concern. Full article

(This article belongs to the Special Issue Metal Additive Manufacturing and Its Post Processing Techniques)

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12 pages, 2588 KiB

Open AccessArticle

Prediction of Surface Roughness of SLM Built Parts after Finishing Processes Using an Artificial Neural Network

by Daniel Soler, Martín Telleria, M. Belén García-Blanco, Elixabete Espinosa, Mikel Cuesta and Pedro José Arrazola

J. Manuf. Mater. Process. 2022, 6(4), 82; https://doi.org/10.3390/jmmp6040082 - 03 Aug 2022

Cited by 8 | Viewed by 2481

Abstract

A known problem of additive manufactured parts is their poor surface quality, which influences product performance. There are different surface treatments to improve surface quality: blasting is commonly employed to improve mechanical properties and reduce surface roughness, and electropolishing to clean shot peened surfaces and improve the surface roughness. However, the final surface roughness is conditioned by multiple parameters related to these techniques. This paper presents a prediction model of surface roughness (Ra) using an Artificial Neural Network considering two parameters of the SLM manufacturing process and seven blasting and electropolishing processes. This model is proven to be in agreement with 429 experimental results. Moreover, this model is then used to find the optimal conditions to be applied during the blasting and the electropolishing in order to improve the surface roughness by roughly 60%. Full article

(This article belongs to the Special Issue Metal Additive Manufacturing and Its Post Processing Techniques)

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22 pages, 5772 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of Maraging Steel Produced Using Hybrid Additive/Subtractive Manufacturing

by Sheida Sarafan, Priti Wanjara, Javad Gholipour, Fabrice Bernier, Mahmoud Osman, Fatih Sikan, Marjan Molavi-Zarandi, Josh Soost and Mathieu Brochu

J. Manuf. Mater. Process. 2021, 5(4), 107; https://doi.org/10.3390/jmmp5040107 - 12 Oct 2021

Cited by 16 | Viewed by 4796

Abstract

Hybrid manufacturing is often used to describe a combination of additive and subtractive processes in the same build envelope. In this research study, hybrid manufacturing of 18Ni-300 maraging steel was investigated using a Matsuura LUMEX Avance-25 system that integrates metal additive manufacturing using laser powder bed fusion (LPBF) processing with high-speed machining. A series of benchmarking coupons were additively printed at four different power levels (160 W, 240 W, 320 W, 380 W) and with the integration of sequential machining passes after every 10 deposited layers, as well as final finishing of selected surfaces. Using non-contact three-dimensional laser scanning, inspection of the final geometry of the 18Ni-300 maraging steel coupons against the computer-aided design (CAD) model indicated the good capability of the Matsuura LUMEX Avance-25 system for net-shape manufacturing. Linear and areal roughness measurements of the surfaces showed average Ra/Sa values of 8.02–14.64 µm for the as-printed walls versus 0.32–0.80 µm for the machined walls/faces. Using Archimedes and helium (He) gas pycnometry methods, the part density was measured to be lowest for coupons produced at 160 W (relative density of 93.3–98.5%) relative to those at high power levels of 240 W to 380 W (relative density of 99.0–99.8%). This finding agreed well with the results of the porosity size distribution determined through X-ray micro-computed tomography (µCT). Evaluation of the static tensile properties indicated that the coupons manufactured at the lowest power of 160 W were ~30% lower in strength, 24% lower in stiffness, and more than 80% lower in ductility relative to higher power conditions (240 W to 380 W) due to the lower density at 160 W. Full article

(This article belongs to the Special Issue Metal Additive Manufacturing and Its Post Processing Techniques)

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14 pages, 6845 KiB

Open AccessArticle

Efficient Finishing of Laser Beam Melting Additive Manufactured Parts

by Henning Zeidler, Rezo Aliyev and Florian Gindorf

J. Manuf. Mater. Process. 2021, 5(4), 106; https://doi.org/10.3390/jmmp5040106 - 09 Oct 2021

Cited by 5 | Viewed by 2350

Abstract

In many cases, the functional performance of additively manufactured components can only be ensured by finishing the functional surfaces. Various methods are available for this purpose. This paper presents a procedure for selecting suitable processes for finishing laser beam melting additive–manufactured parts which is ultimately based on technological knowledge. It was experimentally proven that the use of several consecutive finishing processes is beneficial to achieve better surface quality. One finishing process chain was particularly effective (namely particle blasting/vibratory grinding/plasma electrolytic polishing) and the technological limits of this method were investigated in this study. The optimal parameters for this process combination ensured a surface roughness S_a < 1 µm. Full article

(This article belongs to the Special Issue Metal Additive Manufacturing and Its Post Processing Techniques)

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24 pages, 1507 KiB

Open AccessArticle

Modelling of Powder Removal for Additive Manufacture Postprocessing

by Andrew Roberts, Recep Kahraman, Desi Bacheva and Gavin Tabor

J. Manuf. Mater. Process. 2021, 5(3), 86; https://doi.org/10.3390/jmmp5030086 - 06 Aug 2021

Cited by 2 | Viewed by 2403

Abstract

A critical challenge underpinning the adoption of Additive Manufacture (AM) as a technology is the postprocessing of manufactured components. For Powder Bed Fusion (PBF), this can involve the removal of powder from the interior of the component, often by vibrating the component to fluidise the powder to encourage drainage. In this paper, we develop and validate a computational model of the flow of metal powder suitable for predicting powder removal from such AM components. The model is a continuum Eulerian multiphase model of the powder including models for the granular temperature; the effect of vibration can be included through appropriate wall boundaries for this granular temperature. We validate the individual sub-models appropriate for AM metal powders by comparison with in-house and literature experimental results, and then apply the full model to a more complex geometry typical of an AM Heat Exchanger. The model is shown to provide valuable and accurate results at a fraction of the computational cost of a particle-based model. Full article

(This article belongs to the Special Issue Metal Additive Manufacturing and Its Post Processing Techniques)

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Review

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15 pages, 1791 KiB

Open AccessReview

Tribological Behavior of Additively Manufactured Metal Components

by Raj Shah, Nikhil Pai, Andreas Rosenkranz, Khosro Shirvani and Max Marian

J. Manuf. Mater. Process. 2022, 6(6), 138; https://doi.org/10.3390/jmmp6060138 - 11 Nov 2022

Cited by 25 | Viewed by 3276

Abstract

Additive manufacturing (AM) has recently become an increasingly popular form of production due to its advantages over traditional manufacturing methods, such as accessibility, the potential to produce parts with complex geometry, and reduced waste. For the widespread industry adoption of AM components, metal AM has the most potential. The most popular methods of metal AM are powder-based manufacturing techniques. Due to the layer-by-layer nature of AM, the mechanical and tribological properties of an additive manufactured part differs from those of traditionally manufactured components. For the technology to develop and grow further, the tribological properties of AM components must be fully explored and characterized. The choice of material, surface textures, and post-processing methods are shown to have significant impact on friction and wear. Therefore, this paper focuses on reviewing the existing literature with an emphasis on the development of advanced materials for AM applications as well as the optimization of the resulting surface quality via post-processing and presents areas of interest for further examination in this prospective technology. Full article

(This article belongs to the Special Issue Metal Additive Manufacturing and Its Post Processing Techniques)

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23 pages, 59271 KiB

Open AccessEditor’s ChoiceReview

A Review of Post-Processing Technologies in Additive Manufacturing

by Xing Peng, Lingbao Kong, Jerry Ying Hsi Fuh and Hao Wang

J. Manuf. Mater. Process. 2021, 5(2), 38; https://doi.org/10.3390/jmmp5020038 - 18 Apr 2021

Cited by 96 | Viewed by 13167

Abstract

Additive manufacturing (AM) technology has rapidly evolved with research advances related to AM processes, materials, and designs. The advantages of AM over conventional techniques include an augmented capability to produce parts with complex geometries, operational flexibility, and reduced production time. However, AM processes also face critical issues, such as poor surface quality and inadequate mechanical properties. Therefore, several post-processing technologies are applied to improve the surface quality of the additively manufactured parts. This work aims to document post-processing technologies and their applications concerning different AM processes. Various types of post-process treatments are reviewed and their integrations with AM process are discussed. Full article

(This article belongs to the Special Issue Metal Additive Manufacturing and Its Post Processing Techniques)

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36 pages, 28502 KiB

Open AccessReview

Current Status of Liquid Metal Printing

by Troy Y. Ansell

J. Manuf. Mater. Process. 2021, 5(2), 31; https://doi.org/10.3390/jmmp5020031 - 06 Apr 2021

Cited by 29 | Viewed by 10155

Abstract

This review focuses on the current state of the art in liquid metal additive manufacturing (AM), an emerging and growing family of related printing technologies used to fabricate near-net shape or fully free-standing metal objects. The various printing modes and droplet generation techniques as applied to liquid metals are discussed. Two different printing modes, continuous and drop-on-demand (DOD), exist for liquid metal printing and are based on commercial inkjet printing technology. Several techniques are in various stages of development from laboratory testing, prototyping, to full commercialization. Printing techniques include metal droplet generation by piezoelectric actuation or impact-driven, electrostatic, pneumatic, electrohydrodynamic (EHD), magnetohydrodynamic (MHD) ejection, or droplet generation by application of a high-power laser. The impetus for development of liquid metal printing was the precise, and often small scale, jetting of solder alloys for microelectronics applications. The fabrication of higher-melting-point metals and alloys and the printing of free-standing metal objects has provided further motivation for the research and development of liquid metal printing. Full article

(This article belongs to the Special Issue Metal Additive Manufacturing and Its Post Processing Techniques)

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