Raman microprobe spectroscopy and transmission electron microscopy of thermal sprayed ZrO 2 coatings before and after rub testing of outer air seals

8 wt% Y 2 O 3 –ZrO 2 spray powder and thermally sprayed as thermal barrier coatings on outer air seals were characterized by Raman microprobe spectroscopy (RMS) and transmission electron microscopy to investigate the lateral distribution, composition, structure and grain size of ZrO 2 phases and to separate ZrO 2 and Y 2 O 3 . RMS of transfer layers on ZrO 2 ‐coated shrouds after rub tests against SiC laser‐tipped metallic blades showed the formation of metallic oxides Me I Me II 2 O 4 of spinel type. Wear tracks were partly covered by graphite and spinel‐type oxides. In some cases, the latter were better detectable after laser enhanced cleaning by burning off the covering carbon layer. Copyright © 2001 John Wiley & Sons, Ltd.