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Journal ArticleDOI: 10.1016/J.MSEA.2021.140805

Heat treatment effect on the microstructure, mechanical properties, and wear behaviors of stainless steel 316L prepared via selective laser melting

Abstract: The influence of heat treatment on the microstructure, mechanical properties, and wear behaviors of stainless steel 316L (SS316L) produced via selective laser melting (SLM) was investigated. The fabricated SLM samples were subjected to two different heat treatments: a typical furnace-type heat treatment conducted at 1100 °C for 0.5 h and hot isostatic pressing performed at 1100 °C and 100 MPa for 1.5 h. High-density SLM samples with low porosities were obtained by increasing the laser power and decreasing the scan speed. The heat treatments of the fabricated SLM samples induced the removal of porosity, cellular microstructure, and dense dislocation structures with a slight increase in grain size. In terms of mechanical properties, the fabricated SLM samples exhibited similar hardness and tensile strength properties to those of the conventional SS316L, while a significantly lower elongation was evident. The heat treatments of the fabricated SLM samples improved elongation, while the surface hardness and tensile strength decreased owing to microstructural evolution. During the pin-on-disk test, the conventional SS316L and fabricated SLM sample exhibited similar wear resistance values, which decreased after the heat treatments of the fabricated SLM samples owing to the heat treatment-induced surface softening.

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Topics: Microstructure (53%), Hardness (53%), Ultimate tensile strength (53%) ... read more
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8 results found


Open accessJournal ArticleDOI: 10.1016/J.JMRT.2021.06.027
Abstract: Despite the recent progress in additive manufacturing (AM) process and technology, challenges in the repeatability and reproducibility of AM parts still hinders the adoption of this technique in many industries. This is particularly difficult when a part is qualified on a particular part on a certain machine using optimised parameters. If a manufacturer wishes to expand production to multiple machines, the ability to translate these optimised parameters to different machines much be understood. In this study, four different metal L-PBF printers were used to produce 316L tensile testing samples using the same processing parameters and metal powder supplied from a single batch from the same supplier. In addition to the analysis of the correlation between the input parameters and the output measures, this study reports that despite the same set process parameters, there is significant variations were found in the mechanical performance and properties of the AM samples produced on the different L-PBF metal additive manufacturing machines. For the range of the input processing parameters and the resulting input volumetric energy density applied of 21–37 J/mm3, values of (4–42)%, (200–716) MPa, and (52–214) GPa were obtained for the elongation, ultimate tensile strength and elastic modulus on additively manufactured 316L samples respectively.

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Topics: Tensile testing (52%), Metal powder (52%)

2 Citations


Open accessJournal ArticleDOI: 10.3390/MA14216527
Meet Gor, Harsh Soni, Vishal Ashok Wankhede, Pankaj Sahlot  +3 moreInstitutions (1)
29 Oct 2021-Materials
Abstract: Additive manufacturing (AM) is one of the recently studied research areas, due to its ability to eliminate different subtractive manufacturing limitations, such as difficultly in fabricating complex parts, material wastage, and numbers of sequential operations. Laser-powder bed fusion (L-PBF) AM for SS316L is known for complex part production due to layer-by-layer deposition and is extensively used in the aerospace, automobile, and medical sectors. The process parameter selection is crucial for deciding the overall quality of the SS316L build component with L-PBF AM. This review critically elaborates the effect of various input parameters, i.e., laser power, scanning speed, hatch spacing, and layer thickness, on various mechanical properties of AM SS316L, such as tensile strength, hardness, and the effect of porosity, along with the microstructure evolution. The effect of other AM parameters, such as the build orientation, pre-heating temperature, and particle size, on the build properties is also discussed. The scope of this review also concerns the challenges in practical applications of AM SS316L. Hence, the residual stress formation, their influence on the mechanical properties and corrosion behavior of the AM build part for bio implant application is also considered. This review involves a detailed comparison of properties achievable with different AM techniques and various post-processing techniques, such as heat treatment and grain refinement effects on properties. This review would help in selecting suitable process parameters for various human body implants and many different applications. This study would also help to better understand the effect of each process parameter of PBF-AM on the SS316L build part quality.

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Topics: Process variable (52%)

1 Citations


Journal ArticleDOI: 10.1007/S00170-021-08069-0
Abstract: Combining the geometrical freedom provided by laser powder bed fusion (L-PBF), a powder bed fusion additive manufacturing (AM) process, and tailoring the mechanical properties by the use of lattice structures, many applications benefit from lightweight lattice structures such as aerospace and biomedical. Many different aspects of the lattice structures produced by L-PBF have been addressed in the literature including weight reduction, energy damping, compression behavior, manufacturability, and surface characteristics. Although lattices are seen as a promising design tool, the influence of using lattices inside the part surface on the wear behavior of L-PBF specimens has not yet been addressed in the literature. In this study, the effect of different lattice structures varying in unit cell geometry and size, built along different directions on the wear behavior, is addressed using AISI 316L powder processed with L-PBF. Moreover, to understand the wear behavior in detail, microhardness and compression testing of the samples were accomplished. As a result, it is found that the microhardness measurements change by only 5% on different build directions, whereas the lattice type is a significant factor regarding the modulus of elasticity and absorbed energy per unit volume. Moreover, it is concluded that although the coefficient of friction has an average value of 0.7, it does not vary depending on the tested factors, whereas the specific wear rate is influenced by the build direction and part geometry. Thus, for applications where tribological properties are important, the effect of heat dissipation and cooling rate leading to microstructural changes needs to be considered when utilizing L-PBF.

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Topics: Tribology (50%)

Open accessJournal ArticleDOI: 10.1007/S13632-021-00798-8
Ismat Ara1, Fardad Azarmi1, X. W. Tangpong1Institutions (1)
Abstract: Selective laser melting (SLM) is used to fabricate nearly fully dense 316L stainless steel (SS) samples in this study. A variety of advanced characterization techniques were conducted to identify dominant phases, important crystallographic features, microstructural features, and elemental composition. Porosity of the sample was found to be 0.02% which is the lowest porosity content reported for SLM-processed 316L SS. Microstructural analysis exhibits some columnar grains with epitaxial growth representing complete adhesion between the layers. Existence of some fine cellular grains inside the melt pools is an indication of rapid solidification during the printing process. The strength of this study lies in the addition of new crystallographic information such as lattice parameters of SLM-processed 316L. Finally, using information obtained from the literature, it was possible to better understand the effect of chosen process parameters to achieve nearly fully dense material in the present study.

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Topics: Selective laser melting (57%), Porosity (51%), Microstructure (51%)

Open accessJournal ArticleDOI: 10.3389/FBIOE.2021.778332
Xiaofeng Li1, Yi Denghao2, Xiaoyu Wu1, Jinfang Zhang1  +5 moreInstitutions (4)
Abstract: In this study, seven 316L stainless steel (316L SS) bulks with different angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°) relative to a build substrate were built via selective laser melting (SLM). The influences of different angles on the metallography, microstructure evolution, tensile properties, and corrosion resistance of 316L SS were studied. The 0° sample showed the morphology of corrugated columnar grains, while the 90° sample exhibited equiaxed grains but with a strong texture. The 60° sample had a good strength and plasticity: the tensile strength with 708 MPa, the yield strength with 588 MPa, and the elongation with 54.51%. The dislocation strengthening and grain refinement play a vital role in the mechanical properties for different anisotropy of the SLM-fabricated 316L SS. The 90° sample had greater toughness and corrosion resistance, owing to the higher volume fraction of low-angle grain boundaries and finer grains.

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Topics: Ultimate tensile strength (57%), Microstructure (56%), Grain boundary (55%) ... read more

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64 results found


Open accessJournal ArticleDOI: 10.1007/S11665-014-0958-Z
William E. Frazier1Institutions (1)
Abstract: This paper reviews the state-of-the-art of an important, rapidly emerging, manufacturing technology that is alternatively called additive manufacturing (AM), direct digital manufacturing, free form fabrication, or 3D printing, etc. A broad contextual overview of metallic AM is provided. AM has the potential to revolutionize the global parts manufacturing and logistics landscape. It enables distributed manufacturing and the productions of parts-on-demand while offering the potential to reduce cost, energy consumption, and carbon footprint. This paper explores the material science, processes, and business consideration associated with achieving these performance gains. It is concluded that a paradigm shift is required in order to fully exploit AM potential.

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2,960 Citations


Journal ArticleDOI: 10.1016/J.PMATSCI.2017.10.001
Tarasankar Debroy1, Huiliang Wei1, J.S. Zuback1, T. Mukherjee1  +6 moreInstitutions (4)
Abstract: Since its inception, significant progress has been made in understanding additive manufacturing (AM) processes and the structure and properties of the fabricated metallic components. Because the field is rapidly evolving, a periodic critical assessment of our understanding is useful and this paper seeks to address this need. It covers the emerging research on AM of metallic materials and provides a comprehensive overview of the physical processes and the underlying science of metallurgical structure and properties of the deposited parts. The uniqueness of this review includes substantive discussions on refractory alloys, precious metals and compositionally graded alloys, a succinct comparison of AM with welding and a critical examination of the printability of various engineering alloys based on experiments and theory. An assessment of the status of the field, the gaps in the scientific understanding and the research needs for the expansion of AM of metallic components are provided.

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2,278 Citations


Journal ArticleDOI: 10.1016/J.ACTAMAT.2016.07.019
15 Sep 2016-Acta Materialia
Abstract: Additive Manufacturing (AM), the layer-by layer build-up of parts, has lately become an option for serial production. Today, several metallic materials including the important engineering materials steel, aluminium and titanium may be processed to full dense parts with outstanding properties. In this context, the present overview article describes the complex relationship between AM processes, microstructure and resulting properties for metals. It explains the fundamentals of Laser Beam Melting, Electron Beam Melting and Laser Metal Deposition, and introduces the commercially available materials for the different processes. Thereafter, typical microstructures for additively manufactured steel, aluminium and titanium are presented. Special attention is paid to AM specific grain structures, resulting from the complex thermal cycle and high cooling rates. The properties evolving as a consequence of the microstructure are elaborated under static and dynamic loading. According to these properties, typical applications are presented for the materials and methods for conclusion.

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Topics: Aluminium (50%)

1,782 Citations


Journal ArticleDOI: 10.1016/J.ACTAMAT.2010.02.004
Lore Thijs1, Frederik Verhaeghe1, Tom Craeghs1, Jan Van Humbeeck1  +1 moreInstitutions (1)
01 May 2010-Acta Materialia
Abstract: Selective laser melting (SLM) is an additive manufacturing technique in which functional, complex parts can be created directly by selectively melting layers of powder. This process is characterized by highly localized high heat inputs during very short interaction times and will therefore significantly affect the microstructure. In this research, the development of the microstructure of the Ti–6Al–4V alloy processed by SLM and the influence of the scanning parameters and scanning strategy on this microstructure are studied by light optical microscopy. The martensitic phase is present, and due to the occurrence of epitaxial growth, elongated grains emerge. The direction of these grains is directly related to the process parameters. At high heat inputs it was also found that the intermetallic phase Ti3Al is precipitated during the process.

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Topics: Selective laser melting (61%), Microstructure (56%), Titanium alloy (52%) ... read more

1,729 Citations


Open accessJournal ArticleDOI: 10.1016/J.JALLCOM.2012.07.022
Abstract: The present work shows that optimization of mechanical properties via heat treatment of parts produced by Selective Laser Melting (SLM) is profoundly different compared to conventionally processed Ti6Al4V. In order to obtain optimal mechanical properties, specific treatments are necessary due to the specific microstructure resulting from the SLM process. SLM is an additive manufacturing technique through which components are built by selectively melting powder layers with a focused laser beam. The process is characterized by short laser-powder interaction times and localized high heat input, which leads to steep thermal gradients, rapid solidification and fast cooling. In this research, the effect of several heat treatments on the microstructure and mechanical properties of Ti6Al4V processed by SLM is studied. A comparison is made with the effect of these treatments on hot forged and subsequently mill annealed Ti6Al4V with an original equiaxed microstructure. For SLM produced parts, the original martensite α′ phase is converted to a lamellar mixture of α and β for heat treating temperatures below the β-transus (995 °C), but features of the original microstructure are maintained. Treated above the β-transus, extensive grain growth occurs and large β grains are formed which transform to lamellar α + β upon cooling. Post treating at 850 °C for 2 h, followed by furnace cooling increased the ductility of SLM parts to 12.84 ± 1.36%, compared to 7.36 ± 1.32% for as-built parts.

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Topics: Selective laser melting (57%), Heat treating (56%), Microstructure (55%) ... read more

983 Citations