Investigation of interface, microstructure, and mechanical properties of layered thermal barrier coatings of lanthanum zirconate and YSZ deposited by EB-PVD process

Abstract

Microstructure of the double-layered ceramic thermal barrier coatings of lanthanum zirconate (LZ) and yttria-stabilized zirconia (YSZ) with bond coat on Ni-based superalloy deposited by electron beam evaporation process has been studied. Two sets of combination of LZ and YSZ were deposited: one LZ over YSZ and the other YSZ over LZ. The interfaces of each layer were studied and were found to be sharp; however, some diffusion of elements from below layer was observed. The detailed selected area diffraction of the phases was carried out from the coating cross-section specimens. The LZ layer was mostly found to be amorphous, and fine columnar growth was observed. The YSZ layer over LZ showed two different crystal structures at interface and at the top surface, which were cubic and tetragonal, respectively. The YSZ layers showed clear columnar grains with feather-like intercalated structure Copyright (c) 2014 John Wiley & Sons, Ltd.