Characterization of oxide dispersion strengthened ferritic steel fabricated by electron beam selective melting

Abstract

The solid blocks and walls of the oxide dispersion strengthened (ODS) ferritic steel with nominal composition of Fe–18Cr–2W–0.5Ti–0.3Y2O3 were fabricated by electron beam selective melting (EBSM) method. Processes of melting, grain morphology, tensile properties and fracture behavior of this kind of steel were characterized. It was shown that formation mechanism of columnar grains and equiaxed grains is different during the two scan strategy melting processes. The added nano-scale oxide particles evenly distributed in the molten metal, and the size of these particles did not coarsen during the rapid melting and cooling steps. The ultimate tensile strength of the annealed blocks and walls is superior to the plates with same composition consolidated by powder metallurgy. Especially, wall builds tested parallel to the columnar growth orientation exhibit the outstanding mechanical properties at high temperature owing to the grain anisotropy and uniform distribution of fine Y-rich particles. In addition, the morphology of the individual fracture surfaces demonstrates the grain structure of the cross-section and fracture mode. A certain number of nanoscopic dispersoids are retained in dimples of all the EBSM builds, leading to enhanced strengthening.