In-situ Oxide Film Formation and Enhanced Corrosion Resistance in L-PBF Fabricated 316L Stainless Steel Using SiO<sub>2</sub>-Modified Powders

This study demonstrates that modifying 316L stainless steel powders with nano SiO2 enables the in-situ formation of protective oxide films during Laser Powder Bed Fusion (L-PBF). Through the employment of PDDA, nano-SiO2 particle-modified composite powders were successfully prepared via the agglomeration method. Although the addition of SiO2 slightly reduced powder flowability and decreased the relative density of L-PBF builds, SiO2 could be introduced into the melt pool during L-PBF process. Under the effect of buoyancy and Marangoni convection, the oxide moved towards the melt pool boundary and solidified at the normal surface edge, forming an amorphous oxide film several micrometers thick. Furthermore, core–shell micro-oxides were uniformly dispersed inside the builds. Electrochemical polarization tests in 3.5% NaCl revealed that the in-situ formed oxide film effectively suppressed pit initiation at bead boundaries on the ND surface, resulting in improved corrosion resistance compared with conventional 316L L-PBF builds. These findings demonstrate that SiO2-modified powders provide a viable approach for enabling automatic, in-situ oxide film formation during L-PBF, thereby enhancing the corrosion performance of additively manufactured stainless steels.