PNNL

Abstract

Mechanically alloyed Fe-based alloys with oxide dispersion strengthening have largely dropped out of the marketplace due to high cost, related to problems with complex and unreliable processing. Since these alloys still can have desirable properties, there is incentive to improve processing simplicity and reliability. This research evaluates oxide dispersoid formation during laser powder bed fusion (L-PBF) in atmospheres with different oxygen concentration as an alternative to solid state consolidation and heat treating of novel “chemical reservoir powders.” These powders from a previous study were produced by gas atomization of Fe-15 wt.% Cr with micro-alloyed additions of Y(0.35%), Ti(0.11%), and oxygen (1900ppmw), which was pre-mixed with Ar atomization gas to promote formation of a Cr-oxide powder surface layer. For this study, the Cr-oxide reservoir phase provided dissolved oxygen to promote formation of Y-Ti-rich oxides in the highly turbulent L-PBF melt pool along with controlled oxygen additions from the build chamber atmosphere during melt pool solidification. Using standard L-PBF parameters for 316L builds, the process resulted in formation of oxides with bimodal particle sizes from the 1-10 micron range to the