Ambient pressure fabrication of Ni-free high nitrogen austenitic stainless steel using laser powder bed fusion method

A novel one-step method for fabricating Ni-free high N austenitic stainless steel components at ambient pressure using metal nitride powders as the nitrogen source by the additive manufacturing technology of laser powder bed fusion (LPBF) is demonstrated. It exploits the rapid solidification conditions inherent to the LPBF process for the retention of N in solid solution instead of evaporation. A fully austenitic steel with a high N content of 0.87 wt% has been obtained. The solute strengthening induces more than 70% improvement in hardness and ~ 59% increase in yield strength compared to the LPBF fabricated SS316L and shows promising corrosion resistance. X-ray diffraction, X-ray photoelectron spectroscopy, electron backscattered diffraction were utilized to study the microstructures and relate them to the properties at multi-scales.