Hot corrosion characteristics of Ni-20Cr-18W superalloy in molten salt
(State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China)
Abstract: The hot corrosion behavior of a Ni-20Cr-18W (mass fraction, %) superalloy in the mixture of 75%Na2SO4-25%NaCl melts at 700 and 800 °C was studied. The results demonstrate that the alloy suffers from serious hot corrosion attack in the mixture molten salt. Meanwhile, the degradation of the substrate accelerates with increasing the corrosion temperature. The corrosion layer has an obvious duplex microstructure, and the Cr-depletion zone is detected obviously nearby the inner corrosion layer. The main corrosion products at 700 and 800 °C are almost the same and mainly include NiO, Cr2O3 and Ni3S2, but a trace amount of NiCrO2 is detected at 800 °C for 20 h. The hot corrosion mechanism and formation mechanism of corrosion scales of the Ni-20Cr-18W superalloy in the molten salt are proposed.
Key words: Ni-20Cr-18W superalloys; hot corrosion; molten salt; corrosion mechanism