DEPTH-SELECTIVE DIAGNOSTICS OF THERMAL BARRIER COATINGS INCORPORATING THERMOGRAPHIC PHOSPHORS

摘要

Thermographic phosphors have been previously demonstrated to provide effective non-contact,emissivity-independent surface temperature measurements. Because of the translucent nature of thermalbarrier coatings (TBCs), thermographic-phosphor-based temperature measurements can be extendedbeyond the surface to provide depth-selective temperature measurements by incorporating thethermographic phosphor layer at the depth where the temperature measurement is desired. In this paper,thermographic phosphor (Y2O3:Eu) fluorescence decay time measurements are demonstrated for the firsttime to provide through-the-coating-thickness temperature readings up to 1000°C with the phosphorlayer residing beneath a 100-μm-thick TBC (plasma-sprayed 8wt% yttria-stabilized zirconia). With anappropriately chosen excitation wavelength and detection configuration, it is shown that sufficientphosphor emission is generated to provide effective temperature measurements, despite the attenuationof both the excitation and emission intensities by the overlying TBC. This depth-selective temperaturemeasurement capability should prove particularly useful for TBC diagnostics, where a large thermalgradient is typically present across the TBC thickness.