Behavior of plasma-sprayed thermal barrier coatings during thermal cycling and the effect of a preoxidized NiCrAlY bond coat |
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Authors: | M F J Koolloos J M Houben |
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Affiliation: | (1) Department Mechanical Engineering, Section Thermal Spraying, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands |
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Abstract: | The failure mechanisms of thermal barrier coatings (TBCs) subjected to a thermal load are still not entirely understood. Thermal
stresses and/or oxidation cause the coating to fail and hence must be minimized. During the present investigation, TBCs up
to 1.0 mm were sprayed and withstood high thermal stresses during thermal testing. Owing to the substantial thickness, the
temperature at the top coat/bond coat interface was relatively low, resulting in a low oxidation rate. Furthermore, bond coats
were preoxidized before applying a top coat. The bond strength and the behavior during three different thermal loads of the
preoxidized TBCs were compared with a standard duplex TBC. Finite-element model (FEM) calculations that took account of bond
coat preoxidation and interface roughness were made to calculate the stresses occurring during thermal shock. It is concluded
that the thick TBCs applied during this research exhibit excellent thermal shock resistance and that a preoxidizing treatment
of the bond coat increases the lifetime during thermal loading, where oxidation is the main cause of failure. The FEM analysis
gives a first impression of the stress conditions on the interface undulations during thermal loading, but further development
is required. |
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Keywords: | plasma spraying thermal barrier coatings thermal cycling bond coat oxidation failure mechanism finite element modeling preoxidation ZrO2-Y2O3 |
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