Influence of temperature on hot corrosion behavior of GH4169 superalloy subjected to Na2SO4-NaCl salts attack

This work studies the hot corrosion behavior of GH4169 Ni-based superalloy, deposited with a mixture of salts comprising 95 wt% Na2SO4 and 5 wt% NaCl, across three distinct temperatures (i.e., 650 degrees C, 800 degrees C and 950 degrees C). Corrosion and non-corrosive exposure experiments were compared, yielding data on mass loss and gain, respectively. Material characterization results revealed that the corrosion layer was mainly comprised of Cr2O3, Fe2O3, NiO, Al2O3, TiO2, NbS2 and MoS2. Notably, as the temperature ascended from 650 degrees C to over 800 degrees C, the corrosion mechanisms underwent a transition from pitting to uniform corrosion, corresponding to lowtemperature hot corrosion and high-temperature hot corrosion, respectively. At 650 degrees C, a large number of semi-ellipsoidal corrosion pits manifested on the surface. Conversely, at 800 degrees C and 950 degrees C, the corrosion layer on the surface exhibited nearly uniform spallation. The pit growth model and spallation dynamics model were, respectively, developed based on the observed microstructure features. The models serve as tools for quantitative examination of the hot corrosion process of the superalloy at different temperatures.