Non-destructive evaluation of corrosion degree of thermal barrier coatings using fluorescence

With the increasing application of thermal barrier coatings (TBCs) in marine environments, the failure judgment of TBCs is becoming increasingly important. This paper introduces a method for non-destructive testing of the degree of corrosion of TBCs under alternating high and low temperatures and a Cl−-enriched environment. A Y2O3-8 wt.% ZrO2 + 1 wt% Tb2O3 (YSZ+Tb) coating (where YSZ is yttria-stabilised zirconia) was prepared by atmospheric plasma spraying, and its green fluorescence attributed to the 5D4→7F5 transition of Tb3+ ions was investigated. Moreover, the fluorescence intensity of the YSZ+Tb coating was reduced after corrosion due to a change in the Tb3+ crystal field structure caused by phase transition of the ceramic layer. The relationship between the fluorescence and degree of corrosion of the coating in alternating high and low temperatures was established.