Anisotropic sintering behavior of stainless steel 316L printed by binder jetting additive manufacturing

The influence of sintering temperature and printing orientation on the anisotropic sintering shrinkage of binder jetted (BJ) stainless steel 316L (SS316L) was investigated. Near quasi-isotropic shrinkage behavior with very little anisotropy (≤4%) in the powder bed plane was observed. The out-of-plane anisotropic shrinkage of up to 16% was attributed to the primitive lines formed perpendicular to the build direction. This follows the power law, and the activation energy is not affected by the anisotropy. For all printing orientations, grain boundary diffusion (25-162 kJ/mol) was the dominant sintering mechanism between 1100 °C and 1300 °C. Above 1300 °C, volume diffusion (490-623 kJ/mol) takes over as the dominating sintering mechanism, leading to significantly higher shrinkage up to 15%. The anisotropic shrinkage behavior does not affect the microstructure, as similar evolution of grain sizes, ferrite fractions, and bulk densities (up to 96%) is observed upon sintering.