Hot corrosion product and corrosion layer evolution of La2(Zr0.75Ce0.25)2O7 coating exposed to vanadate-sulfate salts at 1050 °C

Abstract

In this work, plasma-sprayed La2(Zr0.75Ce0.25)2O7 (LCZ) coatings were submitted to hot corrosion tests at 1050 °C in different molten salts: single V2O5 and V2O5 + Na2SO4 mixtures. Several analyses, including XRD, SEM and EDS were employed to characterize the corrosion product and corrosion layer. The hot corrosion behavior of LCZ coating depended on the molten salt. In single V2O5 molten salt, LCZ coatings were corroded for different durations. It was found that (La, Ce)VO4 and m-ZrO2 were formed on the coating surface, independent on duration. The thickness of the corrosion layer increased with increasing duration and then remained unchanged in single V2O5 molten salt. In the mixed V2O5 + Na2SO4 molten salts, the LCZ coating surface was partially corroded and only (La, Ce)VO4 was formed. The morphologies of (La, Ce)VO4 particles have an important relationship with Na2SO4 content. Moreover, the corroded zone can be divided into three layers based on the microstructure and chemical composition. A model which well described the formation mechanism was proposed. These results demonstrated that single V2O5 was more corrosive to LCZ coating than mixed V2O5 + Na2SO4 molten salts.