Stresses within rare-earth doped yttria-stabilized zirconia thermal barrier coatings from in-situ synchrotron X-ray diffraction at high temperatures

Authors

Abstract

There is a growing interest for smart coatings that can be integrated into turbine engines for in-situ temperaturemeasurements or health monitoring. The addition of rare-earth dopants into standard thermal barrier ceramictop coat materials is used to obtain luminescent coatings that enable spectral measurements, for real-timetemperature or health monitoring. The thermomechanical performance and durability of such novel coatingcompositions in extreme environments still remains to be evaluated. Consequently, the ability to manufacturesensor coatings which present suitable thermal properties needs to be demonstrated. For this study, highlyluminescent erbium and europium doped yttria-stabilized zirconia and state-of-the-art yttria-stabilized zirconiacoatings manufactured by air plasma spray were characterized to determine the effects of the embedded rareearth dopants on coating internal strain and stress and to quantify and compare their high temperatureresponse using synchrotron X-ray diffraction. In-situ depth-resolved strain measurements were performed at 15m intervals along the depth of the coatings to evaluate materials response at key locations, specifically at layerinterfaces. In-plane stress was calculated for the coatings and a finite element model was implemented to supplement the results and enable further predictions. The results show that the sensor coatings that were manufactured in this work revealed only minor variations in the strain response of sensor coatings under a typicalthermal cycle and especially at temperatures closer to that of gas turbine operating conditions, compared tostate-of-the-art coatings. This work demonstrates the viability of manufacturing rare-earth doped yttria-stabilizedzirconia coatings that provide beneficial spectroscopic monitoring capabilities while having minimal impact onthe thermomechanical response of the thermal barrier coatings.