High Temperature SO<sub>2</sub>-Gas Corrosion of Ni-Cr-Co Base Superalloy between 800 and 1000°C

Abstract

The Ni-base superalloy, INCONEL740, whose major alloying elements are 24.31 wt.%Cr-20 wt.%Co, was corroded in an Ar-0.2%SO2-gas atmosphere between 800 and 1000oC for 50, and 100 hr in an electric furnace. The scales formed after SO2-gas corrosion tests were generally adherent at 800 and 900oC. At 1000oC, massive scale spallation however occurred over the entire surface. The scales consisted of Cr2O3, (Ni,Co)Cr2O4, and TiO2, indicating that not sulfidation but an oxidation reaction prevailed owing to the thermodynamic stability of concerning oxides.