Hot corrosion behavior of dense CYSZ/YSZ bilayer coatings deposited by atmospheric plasma spray in Na2SO4 + V2O5 molten salts

In this work, the hot corrosion (HC) resistance of bilayer thermal barrier coatings (TBC) architectures composed of dense Ceria-Yttria Stabilized Zirconia (CYSZ) and Yttria-Stabilized Zirconia (YSZ) deposited using the Atmospheric Plasma Spray (APS) technique was evaluated. Two kinds of HC tests were performed using different salt concentrations and thermal cycling (adding fresh salt between cycles) with a constant salt mixture (Na2SO4-V2O5) and constant testing temperature (900 ?). The results showed that the HC mechanism changes with the testing procedure, and the outer dense CYSZ layer acts as a barrier to protect the inner layers against HC degradation. However, the formation of vertical cracks during the coating deposition process affected the corrosion resistance of the TBC systems.