Corrosion and carburization of Ni3Al-based superalloys in high-temperature carbon dioxide

Abstract

To investigate the application of Ni₃Al-based superalloys in gas turbine cycle systems, this experiment exposed Ni₃Al-based superalloys to a 600°C/5 MPa environment with 99.995% pure CO₂ gas. The corrosion and carburization behaviors and mechanisms were investigated in detail. The results reveal that with prolonged thermal exposure, the surface oxides of the samples tend to develop a continuous and homogeneous transition state alumina layer. This layer serves as a protective barrier, preventing the penetration and corrosion of external carbon-containing and oxygen-containing substances into the matrix. A small amount of carbon-containing hazardous substances still penetrates the oxide layer or grain boundaries through highly diffusive pathways such as nanochannels, pores, and cracks, because the transition state of alumina is not completely dense. This leads to carbon deposition at the interface between the oxide layer and the matrix, where a mixture of alumina and amorphous carbon is formed at the interface.