Hot corrosion studies of nanostructured gadolinium zirconate thermal barrier coatings

Improvement of hot corrosion resistance is one of the important parameters governing the lifetime and efficiency of the thermal barrier coatings (TBCs). In this study, the Gadolinium Zirconate (GZ) was synthesized by ball milling method and deposited by Electron Beam-Physical Vapour Deposition (EB-PVD) on Ni-based superalloy substrate with NiCrAlY as an intermediate bond coat. The effect of nanostructured GZ TBCs on hot corrosion resistance were studied under three different salt mixture environments viz; SM1, SM2 and SM3 in isothermal condition at 900 degrees C for 12 h. The results indicated that EB-PVD coated nanostructured GZ TBCs have improved the hot corrosion resistance and performed well under SM1 and SM3 conditions with minimal weight gain and without any spallation, whereas, the TBC suffered severe spallation under of SM2 salt condition with higher weight gain among the other two conditions. The formation of microcracks along the columnar gaps of the topcoat were found in the SM2 condition, have allowed the molten salts infiltration up to the coating interface. The formation of dense corrosive products GdVO4 and m-ZrO2 phases were identified after hot corrosion in SM1 and SM3 condition, which were absent in SM2 condition.

Automated summary

This study investigated the hot corrosion resistance of nanostructured GZ TBCs under three different salt mixture environments, showing that EB-PVD coated GZ TBCs can enhance hot corrosion resistance but may experience spallation or weight gain under certain conditions. Microcracks found in the SM2 condition could lead to molten salt infiltration at the coating interface. The formation of dense corrosive products GdVO4 and m-ZrO2 phases after hot corrosion in SM1 and SM3 conditions, absent in SM2 condition, were identified.