TY  - JOUR
AU  - Ebert, Svenja Maria
AU  - Mücke, Robert
AU  - Mack, Daniel Emil
AU  - Vaßen, Robert
AU  - Stöver, Detlev
AU  - Wobst, Tanja
AU  - Gebhard, Susanne
TI  - Failure mechanisms of magnesia alumina spinel abradable coatings under thermal cyclic loading
JO  - Journal of the European Ceramic Society
VL  - 33
IS  - 15-16
SN  - 0955-2219
CY  - Amsterdam [u.a.]
PB  - Elsevier Science
M1  - FZJ-2013-04420
SP  - 3335 - 3343
PY  - 2013
AB  - 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.
AB  - 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.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000324901800051
DO  - DOI:10.1016/j.jeurceramsoc.2013.06.021
UR  - https://juser.fz-juelich.de/record/138240
ER  -