03 Reactive Atmosphere PBFLB Slag Nanoparticles

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. One of the approaches to manufacture in-situ ODS materials is the use of reactive process gases during powder bed fusion–laser beam (PBF–LB). This study investigates the role of the surface slag layer formed during manufacturing in CO2 atmosphere on the formation of nanoparticles and the underlying layer formation mechanism. A model alloy consisting of pure Fe alloyed with 4.3 wt% Ti was processed in CO2, examining factors such as powder layer height, sample height, and re-melting. The results reveal that nanoparticles do not originate from the slag layer; rather, the slag layer accumulates from liquid nanoparticles rising to the surface of the melt pool until reaching a steady thickness. This research enhances the understanding of particle formation mechanisms in melt pools during additive manufacturing, which is crucial for effectively designing advanced in-situ particle-reinforced ODS materials.