Interface Oxidation Process of ZrO2-8%Y2O3 / CoNiCrAlY Thermal Barrier Coating System

2007 ◽  
Vol 345-346 ◽  
pp. 1035-1038 ◽  
Author(s):  
Hiroyuki Waki ◽  
Akira Kobayashi
Keyword(s):  
Thermal Barrier Coating ◽  
Growth Process ◽  
Thermal Barrier ◽  
Temperature Oxidation ◽  
Electron Probe Micro Analyzer ◽  
Barrier Coating ◽  
Delamination Life ◽  
Tbc Systems ◽  
Tgo Growth ◽  
Y2o3 Layer

Thermal barrier coating (TBC) of a gas turbine blade suffers from high temperature oxidation. It is known that thermally growth oxidation (TGO) grows at the interface between ZrO2- 8%Y2O3 and CoNiCrAlY, and the TGO degrades the adhesive strength. The purpose of this study is to clarify the TGO growth process. Thermal aging tests of ZrO2-8%Y2O3 / CoNiCrAlY TBC systems under various temperature conditions were carried out. TGO growth process was observed by an electron probe micro analyzer (EPMA). Both TGO of Al and TGO of other elements were examined, and the thickness of the TGOs were examined. Results are summarized as follows. (1) The delamination occurred at a ZrO2-8%Y2O3 layer beside the interface. (2) The growth rate of complicated TGO which consisted of Co, Ni and Cr increased with an increase of temperature. However, the complicated TGO wasn’t related with the delamination life. (3) The delamination could occur if the thickness of Al TGO increased more than about 3 μm.

Oxygen Transport Through the Zirconia Top Coat in Thermal Barrier Coating Systems

1998 ◽  
Author(s):  
A.C. Fox ◽  
T.W. Clyne
Keyword(s):  
Thermal Barrier Coating ◽  
Bond Coat ◽  
Ionic Conduction ◽  
Gas Permeability ◽  
Gas Permeation ◽  
Thermal Barrier ◽  
Barrier Coating ◽  
Oxygen Gas ◽  
Plasma Sprayed ◽  
Tbc Systems

Abstract The gas permeability of plasma sprayed yttria-stabilised zirconia coatings has been measured over a range of temperature, using hydrogen and oxygen gas. The permeability was found to be greater for coatings produced with longer stand-off distances, higher chamber pressures and lower torch powers. Porosity levels have been measured using densitometry and microstructural features have been examined using SEM. A model has been developed for prediction of the permeability from such microstructural features, based on percolation theory. Agreement between predicted and measured permeabilities is good. Ionic conduction through the coatings has also been briefly explored. It is concluded that transport of oxygen through the top coat in thermal barrier coating (TBC) systems, causing oxidation of the bond coat, occurs primarily by gas permeation rather than ionic conduction, at least up to temperatures of about 1000°C and probably up to higher temperatures. Top coat permeabilities appreciably below those measured will be required if the rate of bond coat oxidation is to be reduced by cutting the supply of oxygen to the interface.

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