Selective Laser Melting: Materials and Applications

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

Deadline for manuscript submissions: closed (31 August 2019) | Viewed by 35029

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Special Issue Editor

Special Issue Information

Dear Colleagues,

Selective laser melting (SLM) also known as the laser-based power bed fusion process is one of the power-based additive manufacturing techniques that has been widely used to fabricate metallic materials. This process has the capability of processing 3D parts, theoretically, without any shape restrictions with added functionality. There are several aspects that play a crucial role in producing a defect-free component. Some of them are: (1) initial powder quality (composition, particle shape, particle size, particle size distribution, flowability of the powder, etc.); (2) process parameters (laser power, laser scan speed, hatch style, hatch distance, laser spot size, laser focus offset, layer thickness, etc.); and (3) the atmosphere of the chamber (inert gas, its flow rate, the pressure inside the chamber during processing, etc.). Hence, it attracts significant research and warrants a Special Issue devoted to the various aspects of the SLM process.

We are particularly interested in (but not limited to) contributions that focus on topics such as:

  • Alloy design for SLM
  • Novel materials processing including functionally graded materials, amorphous materials, quasicrystalline materials, high entropy alloys, etc.
  • Parameter optimization
  • Microstructural characterization
  • Microstructure–property correlations
  • Process simulations and properties simulation
  • Topological optimization
  • Process development
  • 4D SLM process
  • Applications

Prof. Konda Gokuldoss Prashanth
Guest Editor

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Keywords

  • Selective Laser Melting
  • Alloys
  • Microstructure
  • Properties

Published Papers (7 papers)

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Editorial

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3 pages, 160 KiB  
Editorial
Selective Laser Melting: Materials and Applications
by Konda Gokuldoss Prashanth
J. Manuf. Mater. Process. 2020, 4(1), 13; https://doi.org/10.3390/jmmp4010013 - 18 Feb 2020
Cited by 22 | Viewed by 4074
Abstract
Additive manufacturing (AM) is one of the emerging manufacturing techniques of immense engineering and scientific importance and is regarded as the technique of the future [...] Full article
(This article belongs to the Special Issue Selective Laser Melting: Materials and Applications)

Research

Jump to: Editorial

18 pages, 4039 KiB  
Article
Phase Change with Density Variation and Cylindrical Symmetry: Application to Selective Laser Melting
by Marios M. Fyrillas, Yiannos Ioannou, Loucas Papadakis, Claus Rebholz, Allan Matthews and Charalabos C. Doumanidis
J. Manuf. Mater. Process. 2019, 3(3), 62; https://doi.org/10.3390/jmmp3030062 - 25 Jul 2019
Cited by 1 | Viewed by 2630
Abstract
In this paper we introduce an analytical approach for predicting the melting radius during powder melting in selective laser melting (SLM) with minimum computation duration. The purpose of this work is to evaluate the suggested analytical expression in determining the melt pool geometry [...] Read more.
In this paper we introduce an analytical approach for predicting the melting radius during powder melting in selective laser melting (SLM) with minimum computation duration. The purpose of this work is to evaluate the suggested analytical expression in determining the melt pool geometry for SLM processes, by considering heat transfer and phase change effects with density variation and cylindrical symmetry. This allows for rendering first findings of the melt pool numerical prediction during SLM using a quasi-real-time calculation, which will contribute significantly in the process design and control, especially when applying novel powders. We consider the heat transfer problem associated with a heat source of power Q ˙   ( W / m ) per unit length, activated along the span of a semi-infinite fusible material. As soon as the line heat source is activated, melting commences along the line of the heat source and propagates cylindrically outwards. The temperature field is also cylindrically symmetric. At small times (i.e., neglecting gravity and Marangoni effects), when the density of the solid material is less than that of the molten material (i.e., in the case of metallic powders), an annulus is created of which the outer interface separates the molten material from the solid. In this work we include the effect of convection on the melting process, which is shown to be relatively important. We also justify that the assumption of constant but different properties between the two material phases (liquid and solid) does not introduce significant errors in the calculations. A more important result; however, is that, if we assume constant energy input per unit length, there is an optimum power of the heat source that would result to a maximum amount of molten material when the heat source is deactivated. The model described above can be suitably applied in the case of selective laser melting (SLM) when one considers the heat energy transferred to the metallic powder bed during scanning. Using a characteristic time and length for the process, we can model the energy transfer by the laser as a heat source per unit length. The model was applied in a set of five experimental data, and it was demonstrated that it has the potential to quantitatively describe the SLM process. Full article
(This article belongs to the Special Issue Selective Laser Melting: Materials and Applications)
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15 pages, 4862 KiB  
Article
Dimensional Quality and Distortion Analysis of Thin-Walled Alloy Parts of AlSi10Mg Manufactured by Selective Laser Melting
by Altaf Ahmed, Arfan Majeed, Zahid Atta and Guozhu Jia
J. Manuf. Mater. Process. 2019, 3(2), 51; https://doi.org/10.3390/jmmp3020051 - 21 Jun 2019
Cited by 45 | Viewed by 4804
Abstract
The quality and reliability in additive manufacturing is an emerging area. To ensure process quality and reliability, the influence of all process parameters and conditions needs to be understood. The product quality and reliability characteristics, i.e., dimensional accuracy, precision, repeatability, and reproducibility are [...] Read more.
The quality and reliability in additive manufacturing is an emerging area. To ensure process quality and reliability, the influence of all process parameters and conditions needs to be understood. The product quality and reliability characteristics, i.e., dimensional accuracy, precision, repeatability, and reproducibility are mostly affected by inherent and systematic manufacturing process variations. This paper presents research on dimensional quality and distortion analysis of AlSi10Mg thin-walled parts developed by a selective laser melting technique. The input process parameters were fixed, and the impact of inherent process variation on dimensional accuracy and precision was studied. The process stability and variability were examined under repeatability and reproducibility conditions. The sample length (horizontal dimension) results revealed a 0.05 mm maximum dimensional error, 0.0197 mm repeatability, and 0.0169 mm reproducibility. Similarly, in sample height (vertical dimension) results, 0.258 mm maximum dimensional error, 0.0237 mm repeatability, and 0.0863 mm reproducibility were observed. The effect of varying design thickness on thickness accuracy was analyzed, and regression analysis performed. The maximum 0.038 mm error and 0.018 mm standard deviation was observed for the 1 mm thickness sample, which significantly decreased for sample thickness ≥2 mm. The % error decreased exponentially with increasing sample thickness. The distortion analysis was performed to explore the effect of sample thickness on part distortion. The 0.5 mm thickness sample shows a very high distortion comparatively, and it is reduced significantly for >0.5 mm thickness samples. The study is further extended to examine the effect of solution heat treatment and artificial aging on the accuracy, precision, and distortion; however, it did not improve the results. Conclusively, the sample dimensions, i.e., length and height, have shown fluctuations due to inherent process characteristics under repeatability and reproducibility conditions. The ANOVA results revealed that sample length means are not statistically significantly different, whereas sample height means are significantly different. The horizontal dimensions in the xy-plane have better accuracy and precision compared to the vertical dimension in the z-axis. The accuracy and precision increased, whereas part distortion decreased with increasing thickness. Full article
(This article belongs to the Special Issue Selective Laser Melting: Materials and Applications)
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15 pages, 18269 KiB  
Article
Effect of SLM Build Parameters on the Compressive Properties of 304L Stainless Steel
by Okanmisope Fashanu, Mario F. Buchely, Myranda Spratt, Joseph Newkirk, K. Chandrashekhara, Heath Misak and Michael Walker
J. Manuf. Mater. Process. 2019, 3(2), 43; https://doi.org/10.3390/jmmp3020043 - 02 Jun 2019
Cited by 13 | Viewed by 4399
Abstract
Selective laser melting (SLM) is well suited for the efficient manufacturing of complex structures because of its manufacturing methodology. The optimized process parameters for each alloy has been a cause for debate in recent years. In this study, the hatch angle and build [...] Read more.
Selective laser melting (SLM) is well suited for the efficient manufacturing of complex structures because of its manufacturing methodology. The optimized process parameters for each alloy has been a cause for debate in recent years. In this study, the hatch angle and build orientation were investigated. 304L stainless steel samples were manufactured using three hatch angles (0°, 67°, and 105°) in three build orientations (x-, y-, and z-direction) and tested in compression. Analysis of variance and Tukey’s test were used to evaluate the obtained results. Results showed that the measured compressive yield strength and plastic flow stress varied when the hatch angle and build orientation changed. Samples built in the y-direction exhibited the highest yield strength irrespective of the hatch angle; although, samples manufactured using a hatch angle of 0° exhibited the lowest yield strength. Samples manufactured with a hatch angle of 0° flowed at the lowest stress at 35% plastic strain. Samples manufactured with hatch angles of 67° and 105° flowed at statistically the same flow stress at 35% plastic strain. However, samples manufactured with a 67° hatch angle deformed non-uniformly. Therefore, it can be concluded that 304L stainless steel parts manufactured using a hatch angle of 105° in the y-direction exhibited the best overall compressive behavior. Full article
(This article belongs to the Special Issue Selective Laser Melting: Materials and Applications)
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9 pages, 3619 KiB  
Article
Effect of HIP Treatment on Microstructure and Fatigue Strength of Selectively Laser Melted AlSi10Mg
by Wolfgang Schneller, Martin Leitner, Sebastian Springer, Florian Grün and Michael Taschauer
J. Manuf. Mater. Process. 2019, 3(1), 16; https://doi.org/10.3390/jmmp3010016 - 01 Feb 2019
Cited by 46 | Viewed by 6237
Abstract
This study shows the effect of hot isostatic pressing (HIP) on the porosity and the microstructure, as well as the corresponding fatigue strength of selectively-laser-melted (SLM) AlSi10Mg structures. To eliminate the influence of the as-built surface, all specimens are machined and exhibit a [...] Read more.
This study shows the effect of hot isostatic pressing (HIP) on the porosity and the microstructure, as well as the corresponding fatigue strength of selectively-laser-melted (SLM) AlSi10Mg structures. To eliminate the influence of the as-built surface, all specimens are machined and exhibit a polished surface. To highlight the effect of the HIP treatment, the HIP specimens are compared to a test series without any post-treatment. The fatigue characteristic is evaluated by tension-compression high cycle fatigue tests under a load stress ratio of R = −1. The influence of HIP on the microstructural characteristics is investigated by utilizing scanning electron microscopy of micrographs of selected samples. In order to study the failure mechanism and the fatigue crack origin, a fracture surface analysis is carried out. It is found that, due to the HIP process and subsequent annealing, there is a beneficial effect on the microstructure regarding the fatigue crack propagation, such as Fe-rich precipitates and silicon agglomerations. This leads, combined with a significant reduction of global porosity and a decrease of micro pore sizes, to an improved fatigue resistance for the HIPed condition compared to the other test series within this study. Full article
(This article belongs to the Special Issue Selective Laser Melting: Materials and Applications)
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13 pages, 7891 KiB  
Article
Effect of Build Orientation on the Microstructure and Mechanical Properties of Selective Laser-Melted Ti-6Al-4V Alloy
by Patrick Hartunian and Mohsen Eshraghi
J. Manuf. Mater. Process. 2018, 2(4), 69; https://doi.org/10.3390/jmmp2040069 - 12 Oct 2018
Cited by 46 | Viewed by 6813
Abstract
One of the challenges of additive manufacturing (AM) technology is the inability to generate repeatable microstructure and mechanical properties in different orientations. In this work, the effect of build orientation on the microstructure and mechanical properties of Ti–6Al–4V specimens manufactured by selective laser [...] Read more.
One of the challenges of additive manufacturing (AM) technology is the inability to generate repeatable microstructure and mechanical properties in different orientations. In this work, the effect of build orientation on the microstructure and mechanical properties of Ti–6Al–4V specimens manufactured by selective laser melting (SLM) was studied. The samples built in the Z orientation showed weaker tensile strength compared to the samples built in X, and Y orientations. Samples built in X and Y orientations exhibited brittle fracture features in areas close to the substrate and ductile fracture features in the area farther from the substrate. Defects including pores, cracks, and unmelted/partially-melted powder particles contributed to lower tensile and fracture toughness properties in different orientations. Full article
(This article belongs to the Special Issue Selective Laser Melting: Materials and Applications)
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14 pages, 11740 KiB  
Article
Intra- and Inter-Repeatability of Profile Deviations of an AlSi10Mg Tooling Component Manufactured by Laser Powder Bed Fusion
by Floriane Zongo, Antoine Tahan, Ali Aidibe and Vladimir Brailovski
J. Manuf. Mater. Process. 2018, 2(3), 56; https://doi.org/10.3390/jmmp2030056 - 21 Aug 2018
Cited by 15 | Viewed by 4630
Abstract
Laser powder bed fusion (LPBF) is one of the most potent additive manufacturing (AM) processes. Metallic LPBF is gaining popularity, but one of the obstacles facing its larger industrial use is the limited knowledge of its dimensional and geometrical performances. This paper presents [...] Read more.
Laser powder bed fusion (LPBF) is one of the most potent additive manufacturing (AM) processes. Metallic LPBF is gaining popularity, but one of the obstacles facing its larger industrial use is the limited knowledge of its dimensional and geometrical performances. This paper presents a metrological investigation of the geometrical and dimensional deviations of a selected LPBF-manufactured component, according to the ASME Y14.5-2009 standard. This approach allows for an estimation of both the process capability, as per ISO 22514-4 standard, and the correlations between the part location in the manufacturing chamber and the profile deviations. Forty-nine parts, which are representative of a typical aerospace tooling component (30 mm in diameter and 27.2 mm in height) were manufactured from AlSi10Mg powder using an EOSINT M280 printer and subjected to a stress relief annealing at 300 °C for two hours. This manufacturing procedure was repeated three times. A complete statistical analysis was carried out and the results of the investigation show that LPBF performances for all geometrical variations of 147 identical parts fall within a range of 230 µm at a 99.73% level. Full article
(This article belongs to the Special Issue Selective Laser Melting: Materials and Applications)
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