Dimensional Change of 316 L and Red Mud Composite Manufactured via Binder Jetting: Influence of Green Density Gradient on Sintering Deformation

This study investigates the dimensional change on sintering of products printed via the binder jetting (BJ) additive manufacturing (AM) process, using a powder mixture of stainless steel 316 L and 1 wt% red mud. This research is a part of a vast project aiming to develop continuous-feeding anodes for direct carbon fuel cells (DCFC). Cubes with a through-hole were printed to assess dimensional change during sintering. The geometries of the samples were carefully reconstructed before and after sintering using points acquired by a coordinate measuring machine (CMM). The results reveal a slightly lower shrinkage of the powder mix compared to the reference 316 L material. Novel scaling factors have been proposed to compensate for dimensional changes in future anode production. Additionally, the shape of the cubes was highly distorted after sintering, especially along the powder spreading direction. Finite element simulations reveal the impact of the density gradient in the green state on the origin of sintering deformation. This density gradient, estimated at approximately 0.5% of the relative density per millimeter, is likely caused by the poor flowability of the powder mix.