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RESEARCH PAPERS

Microstructural Investigations of Plasma-Sprayed Yttria Partially Stabilized Zirconia TBC (In Relation to Thermomechanical Resistance and High-Temperature Oxidation Mechanisms)

[+] Author and Article Information
S. Alpérine, L. Lelait

O.N.E.R.A. Materials Science Department, B.P. 72, 92322 Chatillon Cedex, France

J. Eng. Gas Turbines Power 116(1), 258-265 (Jan 01, 1994) (8 pages) doi:10.1115/1.2906802 History: Received February 24, 1992; Online April 24, 2008

Abstract

This study deals with microstructural investigations of plasma-sprayed yttria partially stabilized zirconia thermal barrier coatings, performed by classical and analytical transmission electron microscopy. The aim of the study was to determine eventual relationships between coating microstructure and toughness. The ceramic/metal interface, which plays an important role during TBC thermomechanical solicitation, has also been studied. In the 6–8 wt. percent Y2 O3 range, the metastable tetragonal t′ phase is observed, showing special faulted microstructural features, such as grain twinning and antiphase boundary planes. Moreover, after high-temperature annealing in air, a very fine and stable precipitation of the equilibrium cubic phase appears. It is believed that these microstructural elements could act as crack deviation sites and enhance the coatings’ intrinsic toughness. Microstructural investigations of the alumina scales grown during high-temperature annealing reveal yttrium segregation at oxide grain boundaries as well as significant quantities of zirconium inside the alumina grains. The oxide growth seems to be dominated by a classical grain boundary oxygen diffusion mechanism. The presence of zirconium inside the alumina grains suggests that Al2 O3 also partially forms by chemical reduction of ZrO2 by Al.

Copyright © 1994 by The American Society of Mechanical Engineers
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