Hot corrosion behavior of double ceramic layered CaZrO ₃ /Yttria‐stabilized zirconia coatings

Abstract

Abstract A novel double ceramic layered ( DCL ) CaZrO 3 /Yttria‐stabilized zirconia ( YSZ ) thermal barrier coatings ( TBC s) was designed for improved service life against sulfate vanadate hot corrosion as compared with that of YSZ single layered coating. The hot corrosion behavior of DCL CaZrO 3 / YSZ coatings was studied at 950°C after dry spreading 50%Na 2 SO 4 +50%V 2 O 5 mixture onto a coated surface. The CaZrO 3 as the topmost layer in DCL CaZrO 3 / YSZ coatings, served as a sacrificial layer during sulfate vanadate hot corrosion protecting the underneath YSZ coating. The corrosion reactions in this case were sluggish due to the initial formation of low melting point meta‐calcium vanadate (CaV 2 O 6 ) that isothermally transformed to higher melting point calcium vanadates having higher calcia (CaO) content. The corrosion reaction products sealed the top surface, impeding the oxygen movement and eventually retarded the thermally grown oxide ( TGO ) growth. The sulfate vanadate hot corrosion life of the DCL CaZrO 3 / YSZ coatings was observed to be more than double as compared with single ceramic layered YSZ coatings.