Abstract: The hot corrosion behaviors and mechanisms of DZ792 and DZ792G alloys at 900℃ through 75%Na2SO4+25% NaCl salt deposit were investigated. The results showed that the hot corrosion mechanisms of DZ792 and DZ792G alloys under 900℃ salt deposit were “acidicalkali dissolution/inter sulfideoxide”. During the hot corrosion testing between 70h and 150h， the corrosion mechanism of DZ792G alloy changed from alkali to acidic dissolution mechanism， finally resulting in the catastrophic corrosion for DZ792G alloy， the O2 in molten salt preferentially reacted with the outside Tirich layer at the surface of DZ792 alloy rather than that with inner Cr2O3 layer owing to the high Ti content of this alloy， thus， the mechanism of the hot corrosion changed from alkali to acidic dissolution with the TiO2 reacted with the molten salt consuming the O2. However， because the Ti content of DZ792 alloy was lower than that of DZ792G， the Tirich layer formed in the middle of the multilayered oxide， and the outer Tirich oxide formed stable spinel NiTiO3. The outer Cr2O3 rich oxide layer of the DZ792 reacted with the salt directly， therefore， the further corrosion of DZ792 alloy enable to be inhibited.

Key words: directional solidification Nibase alloys, DZ792, salt deposit, salt mixture, hot corrosion behaviours