Microstructure of Plasma Sprayed La 2 O 3 -Modified YSZ Coatings
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JTTEE5 17:603–607 DOI: 10.1007/s11666-008-9226-9 1059-9630/$19.00 Ó ASM International
Microstructure of Plasma Sprayed La2O3-Modified YSZ Coatings Y. Liu, Y.F. Gao, S.Y. Tao, X.M. Zhou, W.D. Li, H.J. Luo, and C.X. Ding (Submitted May 12, 2008; in revised form August 20, 2008) Yttria-stabilized zirconia (YSZ) has received great attention as a thermal barrier coating (TBC) material for its excellent thermal and mechanical properties. However, the grain growth of YSZ, particularly under temperatures higher than 1200 °C, limits its further applications to a great extent. In our present study, to develop better understanding of the aforementioned phenomenon and explore effective methods to conquer this challenge, TBCs using traditional and La2O3-modified YSZ powders were deposited by atmospheric plasma spraying and their microstructures were investigated. The results show that the La2O3 addition can effectively alleviate the grain growth of coatings under high temperatures.
Keywords
grain growth, heat treatment, microstructure stability, plasma spray, thermal barrier coating
1. Introduction State-of-the-art aircraft and industrial gas turbine engines should operate at as high temperature as possible to maximize their thrust and fuel efficiency. However, the limits of melting point of hot path alloy components in turbines make increasing the temperature difficult. This problem can be facilitated by three principal methods: improved alloy design, cooling by air flow through internal channels cast into the component, and usage of thermal barrier coatings (TBCs), which is generally considered to be the most economic and feasible method (Ref 1-3). TBCs are widely applied on transition pieces, combustion liners, first-stage blades and vanes, combustion chambers, and other hot-path components of gas turbines to enable modern gas turbine engines to operate at gas temperatures well above the melting temperature of the super alloy, thereby improving engine efficiency and
This article is an invited paper selected from presentations at the 2008 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Thermal Spray Crossing Borders, Proceedings of the 2008 International Thermal Spray Conference, Maastricht, The Netherlands, June 2-4, 2008, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2008. Y. Liu, Y.F. Gao, S.Y. Tao, X.M. Zhou, W.D. Li, H.J. Luo and C.X. Ding, Chinese Academy of Sciences, Shanghai Institute of Ceramics, Dingxi 1295, Shanghai 200050, PeopleÕs Republic of China; and Y. Liu, Graduate University of the Chinese Academy of Sciences, Beijing 100049, PeopleÕs Republic of China. Contact e-mail: [email protected].
Journal of Thermal Spray Technology
performance without increasing the surface temperature of the alloy or reducing the requirements for the cooling system. Along with internal cooling of the underlying super alloy component, a 250 lm
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