Thermally grown oxide, a thin layer of mostly aluminum oxide that forms on the bond coat under a thermal barrier as oxygen diffuses through the ceramic. A slow-growing, pure alumina TGO protects the bond coat, but as it thickens over service and mixed oxides appear, stresses at the interface rise until the top coat spalls. TGO thickness is a standard measurement when assessing used hot-section parts.
TGO is up around 8 microns on the trailing edge, that blade's near the end of its coating life.
Also heard as
- thermally grown oxide
- alumina scale
Related terms
Thermal barrier coating
A ceramic coating system that insulates hot-section metal parts from combustion gas temperatures.
MCrAlY
Family of oxidation-resistant alloys of nickel or cobalt with chromium, aluminum and yttrium.
Bond coat
The first layer sprayed on a substrate to help the following coat stick and sometimes protect the metal.
Spalling
Flakes or chunks of coating breaking away from the surface, typically under thermal cycling or impact.