Effect of Morphological Changes in Reused AlSi10Mg Powder on the Formation of Defects in Components Manufactured by SLM

Abstract

The continuous reuse of powder in powder bed additive manufacturing techniques is a common practice, however, research focused on morphological changes in the powder as reuse cycles accumulate is relatively scarce, especially if we consider that the quality of the powder is fundamental to obtain components that meet the requirements of demanding industries such as aeronautics, automotive and medical. The continuous reuses of powder offer two important advantages which are reducing manufacturing costs and waste, both fundamental to the continuity of companies. The repercussions of uncontrolled reuse of powder without understanding the impact on final parts is a growing problem for a common practice. The present study focuses on the morphological changes in the particles of reused powder in five cycles of AlSi10Mg and the resulting effects on the components manufactured by the Selective Laser Melting (SLM) technique, varying manufacturing parameters defined as critical by the literature. Scanning Electron Microscopy (SEM) images of the powder were evaluated following the Zingg methodology, categorizing the particles into four shapes: sphere, disc, rod and blade. 80% of the virgin powder particles showed a spherical morphology, unlike the powder reused in five cycles, where this percentage is reduced by 8%. Elongated particles (blade and rod shape) showed an 11% increase in reused after five cycles. The variation in manufacturing parameters had an impact on the relative density of the components manufactured with reused powder, obtaining a maximum value of 94.5% and a minimum of 86%. The variation in the surface defects of the components was mostly influenced by the power of the laser, the scanning speed and the location of the component in the powder bed, where the sample set with the highest percentage of surface defects was where a laser power of 200 W and a scanning speed of 1000 mm/s and the gas flow was lower due to its location in the powder bed. The results allowed to establish the critical manufacturing parameters for components manufactured with reused powder in five cycles of AlSi10Mg; however, the accumulation of reuse cycles requires further investigation.