Evaluation of hot corrosion behavior of CSZ, CSZ/micro Al2O3 and CSZ/nano Al2O3 plasma sprayed thermal barrier coatings

Abstract

Hot corrosion is one of the main destructive factors in thermal barrier coatings (TBCs) which come as a result of molten salt effect on the coating–gas interface. Hot corrosion behavior of three types of plasma sprayed TBCs was evaluated: usual CSZ, layer composite of CSZ/Micro Al2O3 and layer composite of CSZ/Nano Al2O3 in which Al2O3 was as a topcoat on CSZ layer. Hot corrosion studies of plasma sprayed thermal barrier coatings (TBCs) were conducted in 45wt% Na2SO4+55wt% V2O5 molten salt at 1050°C for 40h. The graded microstructure of the coatings was examined using scanning electron microscope (SEM) and X-ray diffractometer (XRD) before and after hot corrosion test. The results showed that no damage and hot corrosion products was found on the surface of CSZ/Nano Al2O3 coating and monoclinic ZrO2 fraction was lower in CSZ/Micro Al2O3 coating in comparison with usual CSZ. reaction of molten salts with stabilizers of zirconia (Y2O3 and CeO2) that accompanied by formation of monoclinic zirconia, irregular shape crystals of YVO4, CeVO4 and semi-cubic crystals of CeO2 as hot corrosion products, caused the degradation of CSZ coating in usual CSZ and CSZ/Micro Al2O3 coating.