Effects of SO2 on the long-term corrosion behaviour of K452 superalloy

The corrosion behaviour of a nickel-based superalloy K452 in a simulated gas turbine blade service environment (Air+2 vol.% SO2) at 900 °C up to 2000 h was investigated by both microstructural characterization and the Molecular Dynamics (MD) calculations. The mass gain of K452 alloy is increased from 4.12 mg/cm² to 6.64 mg/cm² by the induce of SO2. The formation of numerous voids and pits in the corrosion layer is caused by the presence of SO2. After long-term corrosion, an outer layer with Ni enriches form since the outward diffusion of Ni from the substrate to the outer corrosion layer is promoted by the enhanced chemical potential gradient. The repeated oxidation and sulphidation of Ni-rich sulphides in the outer layer is the main reason for long-term corrosion degradation of the alloy.