Title
Phase distribution in, and origin of, interfacial protrusions in Ni-Cr-Al-Y/ZrO2 thermal barrier coatings
Abbreviated Journal Title
Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process.
Keywords
thermal barrier coatings (TBCs); transmission electron microscopy (TEM); interfaces; microstructure; oxidation; thermal cycling; TEM SPECIMEN PREPARATION; ALUMINA SCALES; LIFT-OUT; OXIDE; BEHAVIOR; DEGRADATION; MECHANISMS; THICKNESS; Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering
Abstract
Interfacial morphology and reaction products in thermal barrier coating systems were investigated by scanning and transmission electron microscopy (SEM and TEM). The samples consist of yttria-stabilized zirconia (YSZ; 6-8 wt.% yttria) deposited by air plasma spraying onto either of two types of bond coats: a layer consisting of Ni-15.9Cr-5.3Al-0.6Y with 5 wt.% of alumina particulate added, or one that was only the base Ni-Cr-Al-Y composition. In samples thermally cycled to failure in a burner rig, numerous interfacial protrusions of several microns or more in size are observed. These have a complex microstructure and contain elemental Ni intermixed with Ni(Al,Cr)(2)O-4 spinel, (Al,Cr)(2)O-3, and other oxides. Unlike some prior studies, nickel oxide (NiO) was not detected. Protrusion microstructures were similar for the two bond coat systems, but interfacial protrusions for the case of the base composition (i.e. no added alumina particulate) did not contain any spinel phase. Comparison of cross-sectional samples before and after oxidation indicates that the protrusions arise from the encapsulation of isolated segments of the bond coat. The intermixing of metallic Ni grains with oxides in the reaction zone may contribute to failure by affecting local stresses during thermal cycling. (C) 2002 Elsevier Science B.V. All rights reserved.
Journal Title
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing
Volume
334
Issue/Number
1-2
Publication Date
1-1-2002
Document Type
Article
Language
English
First Page
65
Last Page
72
WOS Identifier
ISSN
0921-5093
Recommended Citation
"Phase distribution in, and origin of, interfacial protrusions in Ni-Cr-Al-Y/ZrO2 thermal barrier coatings" (2002). Faculty Bibliography 2000s. 3107.
https://stars.library.ucf.edu/facultybib2000/3107
Comments
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