Method for forming a multilayer thermal barrier coating

A method for forming a multilayer thermal barrier coating on an airfoil, the method comprising steps of:

• supporting a rotating airfoil within a vessel that contains members of two different ceramic coating materials and is at least partially evacuated, a first of the ceramic coating materials being characterized by a lower thermal conductivity than a second of the ceramic coating materials;
• sequentially deflecting an electron beam at the members so as to melt a portion of each of the members and thereby produce a vapor of each of the different ceramic coating materials that deposits onto the rotating airfoil, the electron beam being deflected at each of the members for not more than one second, the electron beam being deflected between the members so as to establish a duration of not more than 100 milliseconds during which vapor is not produced from any of the members such that the vapors of the different ceramic coating materials do not coexist within the vessel and a portion of each member is maintained molten, each of the different ceramic coating materials being deposited to form a discrete and homogeneous successive layer on the rotating airfoil such that a distinct interface is formed between each pair of the successive layers with no intermixing of the different ceramic coating materials between the pair of successive layers, wherein multiple pairs of successive layers are deposited, each of the successive layers having a columnar grain structure and a thickness of less than one micrometer.