PHASE EVOLUTION UPON AGEING OF AIR PLASMA SPRAYED t'-ZIRCONIA COATINGS. PT.2. MICROSTRUCTURE EVOLUTION

The correlation between microstructural and phase evolution in aged air plasma-sprayed yttria-partially-stabilised zirconia coatings is discussed. Freestanding coatings with a dense, vertically cracked structure were isothermally aged at 1482 C in air. Characterisation of the resulting microstructur...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 2013-01, Vol.96 (1), p.299-307
Main Authors: Krogstad, J A, Leckie, R M, Kramer, S, Cairney, J M, Lipkin, D M, Johnson, C A, Levi, C G
Format: Article
Language:English
Subjects:
Air plasma
Assessments
Ceramics
Coatings
Evolution
Microstructure
Synchrotrons
Transmission electron microscopy
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Summary:The correlation between microstructural and phase evolution in aged air plasma-sprayed yttria-partially-stabilised zirconia coatings is discussed. Freestanding coatings with a dense, vertically cracked structure were isothermally aged at 1482 C in air. Characterisation of the resulting microstructures was conducted using TEM, and then compared with a parallel analysis of the phase evolution by synchrotron XRD. Additional context was provided by related studies on vapour-deposited coatings. Several salient points can be extracted from these assessments. XRD was further validated as a practical method for studying phase stability after clarification of how the possible phases are defined including: the nature of the t' phase observed in XRD after phase decomposition has begun; and the relationship between the Y-rich tetragonal (t') and Y-rich cubic (c) phases reported to coexist by XRD. A strong relationship between the initial microstructure and the subsequent phase destabilisation is also reported. As a result, phase evolution is proposed to proceed via two competing routes. The interplay between these mechanisms dictates the incubation time for monoclinic formation within a given coating.
ISSN:0002-7820