This paper presents findings of synchrotron diffraction measurements on tubular specimens\nwith a thermal barrier coating (TBC) system applied by electron beam physical vapor deposition\n(EB-PVD), having a thermally grown oxide (TGO) layer due to aging in hot air. The diffraction\nmeasurements were in situ while applying a thermal cycle with high temperature holds at 1000 ..C and varying internal air cooling mass flow and mechanical load. It was observed that, during high\ntemperature holds at 1000 ..C, the TGO strain approached zero if no mechanical load or internal\ncooling was applied. When applying a mechanical load, the TGO in-plane strain (e22) changed to\ntensile and the out of plane TGO strain (e11) became compressive. The addition of internal cooling\ninduced a thermal gradient, yielding a competing effect, driving the e22 strain to compressive and\ne11 strain to tensile. Quantifying TGO strain variations in response to competing factors will provide\na path to controlling the TGO strain, and further improving the lifetime assessment and durability\ndesign strategies for TBC systems.
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