Contents lists available at ScienceDirect Materials Science & Engineering A journal homepage: www.elsevier.com/locate/msea Effect of laser speed, layer thickness, and part position on the mechanical properties of maraging 300 parts manufactured by selective laser melting Adriano Fagali de Souza a,* , Kassim S. Al-Rubaie b , Sabrina Marques c , Bruno Zluhan d , Edson Costa Santos d a Federal University of Santa Catarina (UFSC), Computer Aided Manufacturing Group (GPCAM), Dona Francisca, 8300, Joinville, SC, Brazil b McMaster University, Mechanical Engineering Department, Additive Manufacturing Group – AMG, 1280 Main Street West, Hamilton, Ontario, L8S 4L7, Canada c Federal University of Santa Maria, Presidente Vargas 1958, 96506-302, Cachoeira do Sul, RS, Brazil d SENAI, Innovation Institute for Laser Processing, Albano Schmidt 3333, 89206-001, Joinville, SC, Brazil ARTICLE INFO Keywords: Selective laser melting Maraging steel 300 SLM manufacturing process Mechanical properties ABSTRACT Although selective laser melting technology (SLM) provides significant advantages over conventional manu- facturing processes, it is still a relatively expensive and slow manufacturing method for high-volume production. Increasing the manufacturing speed by optimizing process parameters may increase the porosity of manu- factured parts, thus degrading their mechanical properties. Here, in experimental Phase 1 of the paper, the effect of adjusting the process parameters on the microstructure and properties of maraging steel 300 parts built by SLM has been studied. The porosity, hardness, and roughness were highly dependent on the processing para- meters, whereas the microstructure was not significantly affected. The SLM parameters optimized in Phase 1 were subsequently used in experimental Phase 2 for elucidating the relationships between the part position on the machine table and the final mechanical properties. The part porosity had the greatest effect on the me- chanical properties. A simple analysis of the manufacturing time as a function of the SLM parameters was also performed. 1. Introduction Among the different additive manufacturing (AM) techniques for manufacturing metal parts, the selective laser melting (SLM) is one of the most promising [1]. Yadroitsev and Smurov [2] showed that low porosity (also known as “relative density”) free-form metal parts can be shaped using SLM by sequentially building layers by completely melting a metal powder. Even though high part porosities and long processing times are still major disadvantages compared to the con- ventional manufacturing techniques [3]. Yadroitsev et al. [4] demon- strated that these factors depend on the characteristics of the raw ma- terial (metal powder) and the manufacturing parameters. Liu et al. [5] reported that the microstructure and mechanical properties of SLM- fabricated parts are significantly affected by processing parameters such as scanning speed, power and width of the laser beam, and build orientation. Reducing manufacturing time and costs and keeping the mechanical properties of the manufactured parts are a driving force for SLM development. One of the possibilities is to increase the laser power to allow higher scanning speeds and higher layer thickness. However, this scenario is only useful if low porosity parts can be manufactured [6]. Leuders et al. [7] found that fatigue damage was always initiated by pores located directly beneath the surface, while agglomerations of pores did not cause significant fatigue crack initiation when located within a certain distance from the surface. There has been a tendency for the manufacturers of SLM machines to increase laser power. While the most popular machines are equipped with 100–200 W laser power, it is possible to find devices up to 1000 W [8]. The major challenge in this regard is to increase the scanning speed without increasing the porosity of the manufactured parts. To achieve this, previous studies have focused on investigating the following as- pects of the SLM process: the material, morphology, and grain size of the powder, as well as the layer thickness, hatching pitch, laser power, scanning speed, energy density, and position of parts on the machine table. In most cases, these studies were conducted using laser powers up to 200 W. Studies using higher laser powers are still scarce. Zhang et al. [9] evaluated stainless steel 316L parts built by SLM. The laser power was varied from 80 to 100 W and the scan speed was 300 mm/s. Liverani et al. [10] characterized AISI316L components fabricated by SLM in terms of porosity reduction, tensile strength, and fatigue life, and correlated these properties with the microstructure. https://doi.org/10.1016/j.msea.2019.138425 Received 10 August 2019; Received in revised form 12 September 2019; Accepted 14 September 2019 * Corresponding author. E-mail address: adriano.fagali@ufsc.br (A.F. de Souza). Materials Science & Engineering A 767 (2019) 138425 Available online 16 September 2019 0921-5093/ © 2019 Published by Elsevier B.V. T