Nanoindentation and electron backscatter diffraction mapping in laser powder bed fusion of stainless steel 316L

This study on laser powder bed fusion (L-PBF) of AISI 316 L addresses the anisotropy in microstructure and micro-mechanical properties, from the observation of electron backscatter diffraction (EBSD) and nanoindentation maps in parts made with different volumetric energy densities (VED) and in grains at different crystallographic orientations. Similar experimentation was done with conventionally made AISI 316 L, with the aim of comparing anisotropy and micro-mechanical response. It was observed that the variations of VED, calculated from different process parameters combinations, have an influence on crystallographic oriented grain growth evolution affecting the nanoindentation performance. This progression was responsible of the variation in grain size and average misorientation angles and played important role in determining the micro-mechanical behavior. The highest nanoindentation response was obtained at a VED = 56.67 J/mm3, with an average indentation modulus of 196.77 GPa and hardness of 3.68 GPa. From Texture Pole Figures (PFs) and Inverse Pole Figures (IPFs) of EBSD maps, it was revealed that the highest texture strength of 〈101〉 oriented grains along with the evolution and domain of 〈111〉 oriented grains enhanced the micro-mechanical properties at that VED value. The other causes of this behavior are the relatively lower grain size (11.62 μm) and a higher average misorientation angle (11.74°), when comparing it with rest of the L-PBF AISI 316 L parts. The additional but undesirable strong 〈001〉 texture somehow contributed to the slight mitigation on the micro-mechanical properties in conventional AISI 316 L stainless steels and these parts were found to be comparatively less anisotropic than the parts obtained from L-PBF process.