Two-layer system of a metallic bond coat, usually MCrAlY or aluminide, under a porous ceramic top coat, most often yttria-stabilized zirconia. On air-cooled combustors, transition pieces, blades and vanes it can lower the metal temperature by roughly 100 °C or more, extending life or allowing hotter firing. Thermal barriers are applied by air plasma spray or by electron-beam physical vapor deposition, and their life ends by spalling of the ceramic.
Combustor liners need the thermal barrier coating redone, the dome's showing bare bond coat.
Also heard as
- TBC
- thermal barrier
Related terms
YSZ
Yttria-stabilized zirconia: the standard ceramic for thermal barrier top coats.
Bond coat
The first layer sprayed on a substrate to help the following coat stick and sometimes protect the metal.
TGO
Thermally grown oxide: the alumina layer that grows between bond coat and ceramic in hot service.
DVC
Dense vertically cracked: a thermal barrier sprayed hot so it forms deliberate through-thickness cracks.
Spalling
Flakes or chunks of coating breaking away from the surface, typically under thermal cycling or impact.