Microtexture Analysis of the Alumina Scale in Thermal Barrier Coatings

Transmission electron microscopy‐based grain orientation mapping method was employed to investigate the microtexture of the alumina scale formed in commercial thermal barrier coatings (TBCs) with two standard types of Pt‐enriched bond coats. Reliable orientation/phase maps with a spatial resolution down to 2 nm were acquired on the alumina grains. It was observed that the alumina scale on the Pt‐aluminide β‐phase bond coat has a stronger c‐axis texture normal to the bond coat surface, in comparison with that on the Pt‐diffused γ/γ′‐phase bond coat. The microtexture of the alumina scale could affect its effective coefficient of thermal expansion, which is a contributor to the severity of the bond coat rumpling mechanism of TBCs failure.