Investigation of flowability and spreadability of metal powders for powder bed fusion additive manufacturing

In laser powder bed fusion of metals (PBF-LB/M), thin layers of metal powder are deposited and selectively fused by a laser beam to fabricate solid components. The powder can be applied using various systems, such as a roller, a blade, or a hopper. The characteristics of the powder used have a substantial influence on the quality of the applied powder layer. There are numerous methods for analyzing the flow behavior of metal powder under various test conditions. However, the systematic relationship between the powder flowability metrics, the recoating system, and the recoating speed, as well as their combined influence on the powder bed quality, is not yet fully understood. In this study, three powders with different flow characteristics were tested for their spreading behavior. It was shown that the global roughness of the powder bed, measured with a laser scanner, is a suitable evaluation parameter for the spreadability. Connections were established between the spreadability and the flowability parameters of a powder rheometer and a rotating drum. Moreover, previously unreported interactions between powder properties, recoating system, and recoating speed were observed. Among the investigated systems, the roller recoater consistently produced powder layers with the lowest roughness, largely independent of powder type and recoating speed.