Powder-bed based processing of austenitic stainless steels often results in a columnar microstructure with strong texture caused by a directed solidification of the melt, because of the strong temperature gradient from the heat source perpendicular to the build platform. The resulting anisotropic mechanical properties are undesirable for the majority of applications. In order to avoid columnar grain growth, it is usually attempted to adjust the beam parameters to limit the direction of heat flow parallel to the build direction. Another approach to interrupt epitaxial grain growth is to specifically adapt the alloy to the process conditions.
Günther et al. and Seleznev et al. already observed on EB-PBF manufactured high-alloy austenitic CrMnNi steels with a similar chemical composition, but a slightly different nickel content contrary microstructures and attributed this to the different solidification behaviour of the steels. While the microstructure of CrMnNi steel with lower nickel content was fine-grained and texture-free, the CrMnNi steel with higher nickel content showed a columnar microstructure with a strong texture in build direction. Based on these findings new modified steel variants of steel AISI 304L were developed with the aim to suppress columnar grain growth during the EB-PBF process and produce a fine-grained and texture-free microstructure by changing the chromium and nickel equivalent (Cr_eq/Ni_eq) of this steel. The resulting material properties are discussed on the base of the solidification behaviour by means of thermodynamic calculations as well as microstructural investigations and are compared with steel AISI 304L in its standard composition as well as the properties of the CrMnNi-steel mentioned before. Finally, this work presents requirements for the alloy design of austenitic steels to suppress epitaxial grain growth during the EB-PBF process.