Abstract
In this paper, a detailed assessment of Inconel 718 powder, with varying degrees of degradation due to repeated use in the Laser Powder Bed Fusion (LPBF) process, has been undertaken. Four states of IN718 powder (virgin, used, overflow and spatter) were characterized in terms of their morphology, flowability and physico-chemical properties. Studies showed that used and overflow powders were almost identical. The fine particle-size distribution of the virgin powder, in which 50% of particles were found to be below the nominal particle-size distribution (PSD), was recognized as the main reason for its lower flowability and the main cause of the differentiation between virgin, used and overflow powders. Only spatter powder was found to be degraded enough to preclude its direct LPBF reuse. The oxygen content in the spatter powder exceeded the limit value for IN718 by 290 ppm, and aluminum oxide spots were found on the spatter particles surfaces. Laser absorption analysis showed 10 pp higher laser absorption compared to the other powders. The results of evaluation showed that IN718 powder is resistant to multiple uses in the LPBF process. Due to the low degradation rate of IN718 powder, overflow powder can be re-enabled for multiple uses with a proper recycling strategy.
Highlights
Additive manufacturing (AM) involves layer-by-layer manufacturing methods and has become more and more popular in the last decade
An adjustment of the Laser Powder Bed Fusion (LPBF) process parameters for the U powder is recommended
An evaluation of the metallic powder properties of Inconel 718 was performed in order to detect the level of degradation of powder in different states after repeated use in the Laser Powder Bed Fusion (LPBF) production cycle
Summary
Additive manufacturing (AM) involves layer-by-layer manufacturing methods and has become more and more popular in the last decade. According to the ISO/ASTM 52900:2015 standard, AM has the following seven process categories: Binder Jetting (BJ), Directed Energy Deposition (DED), Material Extrusion (ME), Material Jetting (MJ), Powder Bed Fusion (PBF), Sheet Lamination (SL) and VAT Photopolymerization (VAT). Within those seven categories, more than half use powder as an input material: BJ, DED, MJ and PBF. The benefits of using the LPBF process became evident in the aerospace industry, when the “buy-to-fly” ratio, taking into account and using AM technologies, led to a reduction in the waste of material and a decrease in the amount of energy used [3,4]
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