Improved hot corrosion resistance of plasma sprayed YSZ/Gd2Zr2O7 thermal barrier coating over single layer YSZ

In recent years, research is focused on the development of rare earth zirconates based thermal barrier coatings (TBC). In the present study, bilayered 8 wt% yttria stabilized zirconia (YSZ)/gadolinium zirconate (GZO) TBC system has been developed by atmospheric plasma spraying (APS) process from powders prepared by a single step co-precipitation technique. Hot corrosion behavior of all the coatings are tested in fused Na2SO4 + V2O5 mixture at the concentration of approximately 25 mg/cm(2) at 910 degrees C for 30 h. Formation of gadolinium vanadate (GdVO4) is observed to be the corrosion product in YSZ/GZO bilayer coatings from Energy Dispersive X-ray analysis (EDAX) and is further confirmed by X-ray diffractometry (XRD) analysis. FESEM cross-section analysis of the YSZ/GZO bilayer coating after corrosion test affirms the effectiveness of the bilayer design in preventing the penetration of corrosive salts to the YSZ layer. Also, YSZ/GZO bilayer TBC exhibited a higher thermal cyclic life (300 cycles) than the single layer 8YSZ (175 cycles) coatings at 1100 degrees C.