Long-term behaviour and application limits of plasma-sprayed CeO2- and Y2O3-stabilized ZrO2 thermal barrier coatings

Investigations of changes in phase composition and mechanical
properties of CeO2- and Y2O3-stabilized plasma-sprayed ZrO2-based
thermal barrier coatings (TBC) after long-term heat treatments at
typical service temperatures were performed. Experimental studies
include X-ray diffraction and mechanical testing. TBCs with a high
amount of the tetragonal equilibrium phase t (8 mol% CeO2) show strong
degradation due to the high amount of transformation to the monoclinic
phase and the related decrease in strength. TBCs with a high amount of
tetragonal or cubic non-equilibrium phases t' or c' are more suitable.
Among these, TBCs with higher CeO2-stabilizer contents (19.5 mol-%
CeO2/1.5 mol-% Y2O3 and 35 mol-% CeO2) show less amounts of monoclinic
phase with respect to Y2O3-stabilized TBCs (4.5 mol-% Y2O3), as
commercially used. Therefore they seem to have a high potential for
long-term applications.