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@ARTICLE{Ebert:138240,
author = {Ebert, Svenja Maria and Mücke, Robert and Mack, Daniel
Emil and Vaßen, Robert and Stöver, Detlev and Wobst, Tanja
and Gebhard, Susanne},
title = {{F}ailure mechanisms of magnesia alumina spinel abradable
coatings under thermal cyclic loading},
journal = {Journal of the European Ceramic Society},
volume = {33},
number = {15-16},
issn = {0955-2219},
address = {Amsterdam [u.a.]},
publisher = {Elsevier Science},
reportid = {FZJ-2013-04420},
pages = {3335 - 3343},
year = {2013},
abstract = {Abradable coatings have been used in low- and high-pressure
sections of jet engine compressors for more than 40 years.
Today, they are also used in the high-pressure turbine of
jet engines and are gaining more interest for applications
in industrial gas turbines. They minimise the clearance
between the rotating blade tips and the stationary liners.
Aside from being abradable, the coatings have to be
mechanically stable and withstand high thermo-mechanical
loadings. A typical material used in engines today is
yttria-stabilised zirconia (YSZ). This material
advantageously combines a suitable thermal conductivity with
a high thermal expansion coefficient, but shows a
temperature capability limited to 1200 °C in long-term
applications. Typical abradable coating thicknesses are
above 1 mm. With increasing coating thickness and limited
cooling efficiency leading to high surface temperatures,
there is a risk of premature failure. As a result, new
ceramic materials have been developed with better
high-temperature capability. The present work investigates
an atmospheric plasma sprayed ceramic double-layer coating
system composed of 7YSZ as an intermediate layer and
magnesia alumina spinel as a top layer. This double-layer
system was sprayed onto disc-shaped Inconel 738 superalloy
substrates, which were coated with a vacuum plasma sprayed
MCrAlY bondcoat. The lifetime of the coating system was
assessed via thermal gradient cycling testing with surface
temperatures above 1400 °C. During cycling, the samples
showed a typical failure mechanism with exfoliation of thin
coating lamellae starting from the coating surface. This
failure mechanism was not observed in thermal barrier or
abradable coatings in the past. The failure mechanism was
analysed and mismatch stress calculations were carried out.},
cin = {IEK-1},
ddc = {660},
cid = {I:(DE-Juel1)IEK-1-20101013},
pnm = {122 - Power Plants (POF2-122)},
pid = {G:(DE-HGF)POF2-122},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000324901800051},
doi = {10.1016/j.jeurceramsoc.2013.06.021},
url = {https://juser.fz-juelich.de/record/138240},
}