In-situ decarburization and deoxidation during laser powder bed fusion of water-atomized steel C35

Abstract

Water atomization of low alloyed steels is a very cost-effective way to produce metal powders for laser powder bed fusion. In this study, water atomized C35 steel powder is used to 3D-print samples with different powder bed fusion machines. The porosity of the samples was analyzed. Chemical analysis of printed samples and the powder feedstock was carried out. The gas atmosphere during laser powder bed fusion process was measured to investigate changes in carbon and oxygen content of the samples. With optimal processing parameters, samples with a porosity of only 0.1% can be achieved. Gas atmosphere measurements have shown, that a reaction between carbon and oxygen in the melt pool occurs, leading to the formation of volatile carbon monoxide. By in-situ reduction of the oxygen and carbon level, negative effects caused by oxygen like balling of single melt tracks can be prevented to produce nearly dense parts. • Water-atomized C35 medium carbon steel powder was used for laser powder bed fusion • Samples with porosity of only 0.1% can be built using appropriate parameters • During LPBF, oxygen reacts with carbon inside of the melt pool • Volatile CO forms during LPBF to reduce carbon and oxygen content of samples • Excessive pore formation is prevented due to deoxidation during the process