Contents lists available at ScienceDirect Materials Science & Engineering A journal homepage: www.elsevier.com/locate/msea Tensile properties of selective laser melting products affected by building orientation and energy density Snehashis Pal a, ⁎ , Nenad Gubeljak a , Radovan Hudak b , Gorazd Lojen a , Viktoria Rajtukova b , Jozef Predan a , Vanja Kokol a , Igor Drstvensek a a Faculty of Mechanical Engineering, University of Maribor, Maribor, Slovenia b Department of Biomedical Engineering and Measurement, Technical University of Kosice, Kosice, Slovakia ARTICLE INFO Keywords: Tensile strength Building orientation Energy density Selective laser melting Titanium alloy ABSTRACT Properties of a product fabricated using Selective Laser Melting (SLM) technology depend upon its building orientation as well as Energy Density (ED) used for its fabrication process. As ED is the key factor among all the process parameters in SLM technology, this study has focused on ED along with building orientation. Seven sets of EDs and four sets of building orientations for each set of ED were selected to investigate the dissimilarities among tensile properties as well as other properties of Ti-6Al-4V alloy specimens. The scanning speed was varied to set the different ED values as it influences the thermal characteristics of the molten pool more than the other processing parameters. Tensile strengths of the specimens have differed significantly with respect to building orientations as well as EDs. The tensile characteristics of the specimens have been explored by tensile testing and analyzed regarding metallurgical properties, which are density, porosity, defect, microstructure, and surface morphology. Specimens built in lengthwise vertical position and the energy density of 65 J/mm 3 have shown the best tensile properties in this study. 1. Introduction Since the past few decades, the Selective Laser Melting (SLM) pro- ducts have been widely used for the applications in aerospace, auto- mobile, and biomedical fields [1,2]. However, it is still a challenge to produce a flawless product with intended characteristics [3]. In SLM technology, metal powder having micron-sized diameter particles is melted in the track-by-track and layer-by-layer fashion process using a high-intensity laser in a closed and protected environment [4]. The laser beam in its focus melts the metal powder and the adjacent areas of solidified metal into a tiny melt pool. The melt pool moves forward with the laser beam leaving behind a rapidly cooled solid track. [5,6]. After the laser scans the complete specified area in the powder layer, a new powder layer is deposited on the solidified layer, and the process is repeated until the part defined by the Computer-Aided Design (CAD) model is finished. Several thermal processes including phase transfor- mations occur during melting, fusion and solidification process in SLM [7]. Thus, the orientation of the product in the working space of the machine, as well as the input energy, influence the physical char- acteristics of material in the actioning zone which eventually con- sequences the metallurgical properties of a product as well as a whole product. The melting process of the powder metal, fusion, and its solidifi- cation depend on Energy Density (ED) [6]. ED is volumetric energy input which depends upon laser power, scanning speed, hatch distance, and layer thickness set for a particular production process [8,9]. As per formula, ED is proportional to laser power and inversely proportional to scanning speed, hatch distance, and layer thickness. The properties of a product depend on the ED because it directly influences the melting process, hence the metallurgical and mechanical properties of the product. The characteristics of the molten metallic pool, the process of solidification and bonding with surrounding product segments depend on ED. The liquefied metallic pool may also contain improperly melted powder particles [10], entrapped gaseous bubble [11] and metallic vapour [4]. The spattering of material from the action zone [12] and mentioned contaminations cause improper pool formation, which leads to pore and defect formation. Therefore, different ED results in different porosity and microstructure due to different cooling rates and the number of cycles of reheating and cooling of the consecutively formed layers [13]. The microstructures in vertical and horizontal direction would be dissimilar due to track-by-track and layer-by-layer addition [3,14]. Therefore, the microstructure and other metallurgical https://doi.org/10.1016/j.msea.2018.11.130 Received 7 August 2018; Received in revised form 27 November 2018; Accepted 28 November 2018 ⁎ Correspondence to: Smetanova Ulica 17, 2000 Maribor, Slovenia. E-mail address: snehashis.pal@student.um.si (S. Pal). Materials Science & Engineering A 743 (2019) 637–647 Available online 29 November 2018 0921-5093/ © 2018 Elsevier B.V. All rights reserved. T