U.S. 8,216,687 B2
United Technologies Corporation has been granted a patent for an article comprised of a metallic substrate; a coating system atop the substrate and comprised of an alumina-chromia layer having a thickness at least 50% of a total thickness of the system; and a bondcoat between the substrate and the alumina-chromia layer.
Source:
http://www.coatingsworld.com/issues/2013-03/view_patents/united-technologies-patents-thermal-barrier-coating/
