Thermal Conductivity and Water Vapor Stability of Ceramic HfO2-Based Coating Materials

2004·15.7 MB·English

by  Zhu, Dong-Ming

A paper abstract to be submitted to
The 105th Annual Meeting & Exposition of The American Ceramic Society
April 27 - 30,2003, Nashville, Tennessee
Thermal Conductivity and Water Vapor Stability of Ceramic Coating Materials
A
Dongming Zhu, Dennis S. Fox, Narottam P. Bansal and Robert A. Miller
NASA John H. Glenn Research Center
Cleveland, Ohio 44135
HfQ-Y203 and La2Zr207 are candidate thermal/environmentalb arrier coating materials
for gas turbine ceramic matrix composite (CMC) combustor liner applications because of their
relatively low thermal conductivity and high temperature capability. In this paper, thermal
conductivity and high temperature phase stability of plasma-sprayed coatings and/or hot-pressed
Hf02-5mol%Y203, HiQ- 15 mol%Y203a nd La2Zr207 were evaluated at temperatures up to
1700°C using a steady-state laser heat-flux technique. Sintering behavior of the plasma-sprayed
coatings was determined by monitoring the thermal conductivity increases during a 20-hour test
period at various temperatures. Durability and failure mechanisms of the Hf02-Y203 and
LazZr207 coatings on mullite/SiC Hexoloy or CMC substrates were investigated at 1650°C under
thermal gradient cyclic conditions. Coating design and testing issues for the 1650°C
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