Abstract
The morphology and composition of the thermally grown oxide (TGO) layer in a thermal barrier system with a NiCoCrAlY bond coat are characterized by a combination of scanning and transmission electron microscopy, focused ion beam sectioning and energy-dispersive spectroscopy (EDS) element mapping. The investigation has revealed a complex TGO that exhibits numerous thickness inhomogeneities ('pegs'), and a sizable distribution of nano-scale second phase particles. These particles have been determined to be of two types: regions of entrained bond coat and oxides based on Y2O3 and HfO2. The most probable phase makeup of the oxides is a cubic fluorite of approximate composition 4HfO2-Y2O3. Diffusion of Hf and Y from the bond coat or entrapment of bond coat elements during TGO growth are the most likely mechanisms for the formation of these oxide particles.
Original language | English (US) |
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Pages (from-to) | 1495-1502 |
Number of pages | 8 |
Journal | Surface and Coatings Technology |
Volume | 201 |
Issue number | 3-4 |
DOIs | |
State | Published - Oct 5 2006 |
All Science Journal Classification (ASJC) codes
- General Chemistry
- Condensed Matter Physics
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Materials Chemistry
Keywords
- Energy-dispersive spectroscopy
- Fluorite
- Hafnia
- NiCoCrAlY
- Thermal barrier coatings
- Thermally grown oxide