Anisotropic response of additively manufactured 316 L stainless steel towards low-temperature gaseous carburization

In order to modify the surface properties of austenitic stainless steel fabricated by Laser Powder Bed Fusion (LPBF), low-temperature gaseous carburization (LTGC) was employed. During LTGC, a carburized case of expanded austenite forms at the surface, which contains a high surface carbon content (-2.5 wt%), high nano hardness (-12.6 GPa), large compressive residual stresses (from-2.4 GPa to-3.2 GPa), and is free of carbide precipitates. In the expanded austenite zones, different residual stresses were measured with X-ray diffractometry (XRD) for the top plane, i.e. in the plane perpendicular to the build direction, and for the side plane. This anisotropy is suggested to be caused by grain-shape anisotropy for the different specimen planes and inherent to the hierarchical microstructures resulting from L-PBF.

Automated summary

Low-temperature gaseous carburization (LTGC) was used to modify the surface properties of austenitic stainless steel fabricated by Laser Powder Bed Fusion (LPBF). During LTGC, a carburized case of expanded austenite forms at the surface, which has high surface carbon content (-2.5 wt%), high nano hardness (-12.6 GPa), large compressive residual stresses (from-2.4 GPa to-3.2 GPa), and is free of carbide precipitates. X-ray diffractometry (XRD) measurements showed anisotropic residual stresses in the expanded austenite zones, which are suggested to be caused by grain-shape anisotropy and hierarchical microstructures resulting from L-PBF.