ISSN:
1573-4889
Keywords:
thermal barrier coating
;
TEM
;
aluminum oxide scales
;
scale adhesion
;
spallation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The structure and chemistry of the thermally grown oxide scale in a thermalbarrier coating having an electron beam-physical vapor depositedyttria-partially stabilized zirconia (YPSZ) topcoat and aplatinum–nickel–aluminide (Pt–Ni–Al) bondcoat werestudied using transmission electron microscopy. The scale consisted ofhexagonal aluminum oxide (α-Al2O3) in both as-coated and thermallycycled specimens; no metastable Al2O3 polymorphs were observed. In as-coatedspecimens, the scale's grains had a fine, columnarmorphology. ZrO2-rich dispersoids were observed both intra- andintergranularly throughout the scale. Thermally cycled specimens had aduplex scale structure: one band of grains adjacent to the YPSZ had anequiaxed morphology and contained ZrO2-rich dispersoids; a second band ofdispersoid-free grains adjacent to the bondcoat had a coarse, columnarmorphology. Porosity and cracks were associated with the interface betweenthe bands. The formation of the banded morphology and the cracking areproposed to be associated with the presence of the ZrO2-rich dispersoids.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1004646227870
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