Adherence and Failure of an EBPVD 7YSZ Coating on a β/γ-NiCrAl Substrate: A Pilot Study

Oxidation, lifetime and crack path at failure upon furnace oxidation testing at 1100 °C were evaluated for an undoped alumina-forming NiCrAl alloy/7YSZ (7 wt% yttria stabilized zirconia) coating system. The coating was deposited by electron beam physical vapor deposition (EBPVD). The thermally grown oxide (TGO) was investigated by energy dispersive spectroscopy. The outer zone of the TGO comprised a particular interlayer-denominated mixed zone (MZ), which revealed accumulation of Cr together with Y and Zr. The contents of Y and Zr in the MZ of the undoped sample were in good agreement with compositional data previously evaluated for thermal barrier coating (TBC) systems with EBPVD NiCoCrAlY bond coats versus relative lifetime. These data are considered characteristic measures of the stage of life for EBPVD TBC systems.