Cyclic hot corrosion failure behaviors of EB-PVD TBC systems in the presence of sulfate and vanadate molten salts

Abstract

The cold gas dynamic spray (CGDS) method has been considered a promising technology to produce a metallic bond coat for thermal barrier coating (TBC) systems. In this study, CoNiCrAlY bond coats produced by CGDS method were coated with yttria-stabilized zirconia (YSZ) by electron beam physical vapor deposition (EB-PVD). TBCs were subjected to 50 wt % V 2 O 5 and 50 wt % Na 2 SO 4 molten hot corrosion salt combinations at 1000 °C. In the case of YSZ top coat on TBCs, the reaction between Na 2 SO 4 , V 2 O 5 , and Y 2 O 3 salts generates YVO 4 crystals, and these structures cause the transformation of tetragonal ZrO 2 to monoclinic ZrO 2 . This situation occurs under operating conditions that lead to TBC failure. Hot corrosion behavior and the related failure mechanisms of TBC systems were investigated and discussed using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis, and X-ray diffractometer (XRD).