Thermal Cycle Resistance of Yttria Stabilized Zirconia Coatings Prepared by MO-CVD

Abstract

Yttria stabilized zirconia (YSZ) coatings containing 0 to 9.5 mol% Y₂O₃ were prepared on Hastelloy-XR alloys by metal-organic chemical vapor deposition (MO-CVD), and the effect of Y₂O₃ content on thermal cycle resistance was investigated in the temperature intervals from 600 to 1273 K and from 600 to 1373 K in air. In the 600–1273 K interval, delamination after 1200 cycles had not occurred for any of the Y₂O₃ contents of YSZ coatings. In the 600–1373 K interval, the YSZ coatings containing 0, 0.5 and 9.5 mol% Y₂O₃ suffered partial delamination after 1200 cycles, while no delamination was observed for the YSZ coatings containing 4 mol% Y₂O₃. During the thermal cycles, thermally grown oxide (TGO) layers consisting of inner Cr₂O₃ and outer (Ni,Mn,Fe)(Fe,Cr)₂O₄ spinel were formed at the YSZ coating/Hastelloy-XR substrate alloy interface. The delamination of YSZ coatings occurred at the alloy side near the TGO layer/Hastelloy-XR alloy interface.