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Phases in Plasma Sprayed Thermal Barrier Coatings from Yttria Partially Stabilized Zirconia
Author(s) -
Cosack T.,
Kopperger B.
Publication year - 2001
Publication title -
materialwissenschaft und werkstofftechnik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.285
H-Index - 38
eISSN - 1521-4052
pISSN - 0933-5137
DOI - 10.1002/1521-4052(200108)32:8<678::aid-mawe678>3.0.co;2-h
Subject(s) - thermal barrier coating , cubic zirconia , monoclinic crystal system , materials science , yttria stabilized zirconia , tetragonal crystal system , phase (matter) , ceramic , chemical engineering , composite material , crystallography , chemistry , crystal structure , organic chemistry , engineering
The application of thermal barrier coatings (TBC) is increasing in aeroengines. Surface temperatures up to 1450°C require the application of ceramic TBCs because the temperature capability of metallic substrate materials is not high enough. The service life of turbine components could be improved by the use of yttria partially stabilized zirconia top coatings. The most successfull TBCs are made from 7–9 wt‐% yttria partially stabilized zirconia. One of the most discussed reasons of damages of such TBCs is the transformation between monoclinic and tetragonal phase in zirconia in connection with a dramatic change in volume. Thus in this work resulting phases of plasma sprayed zirconia coatings were investigated. It was found that no monoclinic phase could be detected after heat treatments at 1300, 1400 and 1466°C with cooling rates > 2°/min. Only with cooling rates < 2°/min monoclinic phases occured. It can be concluded that the metastable tetragonal high temperature configuration of yttria partially stabilized zirconia is “very stable”. The conditions in aeroengines with cooling rates > 2°C prevent the formation of the monoclinic phase in zirconia.