Mechanisms of spallation of electron beam physical vapor deposited thermalbarrier coatings with and without platinum aluminide bond coat ridges

Grain boundary ridges, that form on the surface of platinum aluminide [(Ni, Pt)Al] bond coats prior to the deposition of the yttria stabilized zirconia ceramic layer by the electron beam physical vapor deposition (EB-PVD) proc ess, were shown to be the sites for spallation damage initiation in (Ni,Pt) Al/EB-PVD thermal barrier coatings. When these ridges are removed prior to deposition of the ceramic layer, a 3 x Life improvement is achieved. This study compares the spallation mechanisms in specimens with and without bond coat ridges, in order to explain the improvement in spallation life. (C) 2 000 Elsevier Science B.V. All rights reserved.