PSI - Issue 23

Anton Zhukov et al. / Procedia Structural Integrity 23 (2019) 305–309 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction

Methods for manufacturing parts of complex shape according to designed digital models by melting with concentrated energy streams in layers of powdered raw materials are intensively developed and improved (Gibson et al. (2016), Shishkovsky (2016), Grigoriev et al. (2016)), which indicates the relevance of the presented work. Among additive methods using energy sources of different nature, the principal difference in the process of selective laser melting (SLM) is the short-term effect of a laser beam on microvolumes in which the solid and liquid phases interact with each other under conditions of strong thermodynamic disequilibrium. In SLM technology, local acts of melting and crystallization are characterized as transient modes in multi-period phenomena of heat conduction and are not well understood. Therefore, in numerous studies in this area, much attention is paid to the study of the structure and properties of the resulting metallic objects. For example, in Tarasova (2010), the prospects of using laser radiation in increasing the wear resistance of steels are shown, in Barakhtin et al. (2017), Tarasova et al. (2015) and Abele et al. (2015), the influence of the SLM process modes on the structure and physicomechanical properties of superalloys based on cobalt and steels of different chemical composition is noted. In Zhukov et al. (2017), it was assumed that in SLM steels of different chemical composition, the local chemical heterogeneity to the greatest extent determines the features of the structure and complex of mechanical properties. The aim of the presented work was to obtain data on the morphology of the structure of samples obtained by the SLM method from iron powder manufactured by melt spraying (atomization). 2. Materials and experimental methods We used porous technical iron powder containing manganese (0.08 ± 0.06 wt. %) and silicon (0.07 ± 0.03 wt. %) impurities. The powder was manufactured on the HERMIGA 75/IV unit by melt spraying (atomization). The granulometric composition of the powder was determined on a Malvern Mastersizer 2000 unit using laser diffraction. A spherical shape and a particle size of up to 200 µm characterized the resulting powder. Then, the fraction of the powder suitable for u se in the SLM technology <80 µm was screened out, the proportion of usable powder was 70 %. The SLM process was implemented on the EOSINT M270 unit. As a model, a cylinder Ø12.6x10 mm was chosen, which was increased along the axis direction by alternating operations of forming a layer 40 μm thick from sifted raw materials and subsequent melting of the powder with a 195 W laser beam with a scanning speed of 800 mm / s (Fig. 1). Under the control of the computer, the processes of feeding the powder and scanning the melting zone with a laser beam are realized in a nitrogen atmosphere.

Fig. 1. The scheme of the EOSint M270 unit.