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5168 |
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Thursday, June 08, 2017, Hall 12 3:40 PM Aviation & Power Generation Industry IV |
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Characterization of bondcoat roughness profiles and effects on thermal barrier coating-lifetime |
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Georg Mauer* / Forschungszentrum Jülich GmbH, Germany Karl-Heinz Rauwald / Forschungszentrum Jülich, IEK-1, Germany Philipp Terberger/ Forschungszentrum Jülich, IEK-1, Germany Robert Mücke/ Forschungszentrum Jülich, IEK-1, Germany Daniel E. Mack/ Forschungszentrum Jülich, IEK-1, Germany Robert Vaßen/ Forschungszentrum Jülich, IEK-1, Germany |
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The lifetime of thermal barrier coating systems is considerably dependent on the bondcoat properties which on the other hand are strongly influenced by the manufacturing process. The thermal spray method, process parameters and feedstock characteristics determine important features such as oxygen content and roughness profiles. To characterize the latter quantitatively with respect to the coating system-lifetime, vertical parameters like the arithmetic mean roughness (Ra) were found to be insufficient in previous studies. In this work, bondcoats were manufactured using different thermal spray methods like LPPS, APS and HVOF as well as different cuts of powder feedstock. Particular importance was attached to the combination of basic coatings and special top layers sprayed with different methods and/or feedstock, so called flash coats. The life-time performance was investigated by isothermal and temperature gradient tests and correlated with characteristic values of the roughness profiles obtained from fractal analysis. By this approach, the surface morphology is described in vertical as well as in horizontal extent. The results allow to assess roughness characteristics with respect to thermal barrier coating-lifetime and to choose appropriate spray methods and feedstock powder cuts. |