Improving the Hot Corrosion Resistance of Nanostructured ZrO2-7wt.%Y2O3 Thermal Barrier Coatings Fabricated by Plasma Spraying

Abstract

Conventional and nanostructured ZrO2-7wt.%Y2O3 thermal barrier coatings (TBCs) were prepared by plasma spraying technology. Microstructure and hot corrosion resistance of two TBCs in 75%Na2SO4+25%NaCl (mass fraction) mixed molten salt under 850 °C were compared. Meanwhile, hot corrosion failure mechanisms of TBCs were investigated. Results demonstrated that both conventional and nanostructured TBCs were typical lamellar stacking characteristic. However, compared with conventional TBC, the nanostructured TBC presented the base phase which is gained from recrystalization of fully melted nano-particles as well as the embedding phase of partially melted nano-particles. The nanostructured TBC has lower porosity and higher density. For both conventional and nanostructured TBCs, hot corrosion failure is caused by partial transformation of tetragonal phase (t-ZrO2) into monoclinic-phase (m-ZrO2) martensite as a response to the consumption of the stabilizer Y2O3. However, the nanostructured TBC generally has lower degree of hot corrosion and better protection to the metal bonding layer and matrix compared with conventional TBC.