Einfluss der Bondcoatzusammensetzung und Herstellungsparameter auf die Lebensdauer von Wärmedämmschichten bei zyklischer Temperaturbelastung

Subanovic, Marko

Book	PreJuSER-136189

Einfluss der Bondcoatzusammensetzung und Herstellungsparameter auf die Lebensdauer von Wärmedämmschichten bei zyklischer Temperaturbelastung

Subanovic, M. (Corresponding author)FZJ*

2009
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-89336-582-1

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Schriften des Forschungszentrums Jülich. Reihe Energie und Umwelt / Energy und Environment 42, 188, VI S. (2009) = RWTH Aachen, Diss., 2008

Please use a persistent id in citations: http://hdl.handle.net/2128/3708

Abstract: In the present study the influence of the bond coat composition on the lifetime of thermal barrier coatings during thermal cycling was investigated. The knowledge, that the reactive elements (RE), which are essential for the improvement of the oxide scale adhesion, are “lost”, during the bond coat processing, made it necessary to investigate systematically the influence of the different manufacturing stages on the RE distribution. After VPS (vacuum plasma spraying) with a high oxygen partial pressure in the spraying chamber, the reactive elements in the NiCoCrAl-coating were tied up in oxide precipitates, and thus their beneficial effect on the scale adhesion was inhibited. Another important observation is that the RE’s are depleted during the bondcoat vacuum heat-treatment. The degree of Y-depletion depends not only on the Y-reservoir in the coating (Y-content and thickness) but also on the heat-treatment parameters, such as vacuum quality and temperature. A thin, dense alumina oxide scale with a smooth interface between bond coat and TGO doesn’t necessary lead to a lifetime extension of the EB-PVD TBC’s. TBC’s with such oxide morphology typically failed due to crack formation and propagation along the interface between the TGO and the bondcoat. By addition of zirconium it was possible to shift the failure initiation from the interface TGO/bondcoat to the interface TBC/TGO, which can apparently accommodate more thermal strain energy before failure. The shift of the failure location was achieved by a change of the oxide morphology, which mainly relies on adjusting a non-even wavy interface between the TGO and the bond coat and formation of defected oxide layers. In contrast, a defected oxide scale with a high growth rate shortened the life time of APSTBC’s. Porosity and spinel formation weakened the mechanical integrity of the oxide scale, and facilitated the crack formation and propagation of the already existing cracks. The potential to improve lifetimes of APS-TBC’s should arise from an adjustment of optimal interface roughness between TBC and bond coat, a TBC morphology with defect perpendicular to the crack propagation direction, formation of oxide scales with a low defect density and growth rate, “strong” interface between bond coat and oxide. [...]

Keyword(s): turbine blade ; bonding ; heat ; corrosion inhibition ; thermal barrier coating ; insulation ; Boncoat ; Wärmedämmschichten ; metallische Haftvermittlerschichten