Effect of microstructure on hot corrosion behavior of new superalloy Ad 730 in 75 wt% Na2SO4 + 25 wt% NaCl molten salt

Abstract

The new superalloy Ad 730 samples of three different microstructures were prepared by heat treatment and then exposed to a 75 wt% Na2SO4 + 25 wt% NaCl salt at 973 K for 30 h. Compared with the samples with larger grain sizes and fewer γ’ phases, the initial sample (HT) had a denser oxide layer and suffered less hot corrosion damage. The fine-grained structure in HT accelerates the diffusion of Cr to form protective oxides and provides more oxide nucleation sites. The more γ’ phases in HT inhibit the diffusion of hot corrosion.