Microstructure characterization and mechanical properties of laser additive manufactured oxide dispersion strengthened Fe-9Cr alloy

Abstract

Oxide dispersion strengthened (ODS) alloys are attractive material candidates for advanced fission and fusion reactor application owing to their excellent radiation tolerance and high temperature creep strength but traditional manufacturing process encounters some difficulties in producing complex components. An ODS Fe-9Cr alloy with nominal composition of Fe-9Cr-1.5W-0.3Ti-0.3Y (wt%) were manufactured by laser engineered net shaping (LENS) method with different laser power. Equiaxed martensitic grains together with micro-pores were observed in the as-deposited alloys. With the increase of laser power, the density and size of pores decrease, the grain size of the alloys increases while the number density of nanoscale oxides decreases due to the formation of thicker Y-Ti-O-enriched and Al-O-enriched slag layer in the block surface. Hot isostatic pressing (HIP) processing of the as-deposited ODS alloy with low laser power reduces significantly the density of and the size of micro-pores, refines the grain size, and precipitates higher density of nanoscale oxides (Y2TiO5 and Y2Ti2O7), which improves significantly the tensile properties that is comparable at room temperature and is better at 873 K than ODS EUROFER steel produced by conventional powder metallurgy.