Studying the formation of nodules in a Ni-Fe-Cr based superalloy used in fireside corrosion under the impact of creep stress

Creep rupture tests on a Ni-Fe-Cr based superalloy were conducted in a custom-built rig at 750 °C under simulated fireside corrosion environment. The impact of creep stress on corrosion was investigated by controlling load level (without loading, loads of 120–195 MPa). The phase composition, microstructure, and morphology of surface corrosion products and corrosion-affected area were studied. The mechanism responsible for the production of surface nodules and the observed uniform oxide scale during fireside corrosion are discussed. Results show that the presence of creep stress promotes the development of surface nodules and increases the corrosion-affected area.