Relationship between slag layer and in-situ nanoparticle formation in PBF–LB using reactive atmospheres

Oxide dispersion strengthened (ODS) materials are typically processed using powder metallurgy routes or additive manufacturing to ensure homogeneous nanoparticle distribution in the materials. Processing routes where the nanoparticles are formed during manufacturing (in-situ) can effectively prevent problems occurring in ex-situ routes such as nanoparticle agglomeration. This study focuses on the in-situ manufacturing of ODS materials using reactive process gases during powder bed fusion–laser beam (PBF–LB) and examines the effects of carbon dioxide (CO2) on nanoparticle formation and slag layer development. A model alloy of pure Fe alloyed with 4.3 wt% Ti was processed in CO2 to investigate the influence of powder layer height, sample height, and re-melting on nanoparticle and slag layer formation. The results revealed that nanoparticles do not originate from the slag layer; instead, the layering develops as liquid nanoparticles float to the surface of the melt pool, accumulating until reaching a steady thickness. This research contributes to understanding particle formation mechanisms in additive manufacturing processes, essential for defining alloy design requirements for advanced in-situ particle-reinforced ODS materials.