Characterization of commercial EB-PVD TBC systems with CVD (Ni,Pt)Al bond coatings

Failure of electron-beam physical vapor deposition (EB-PVD) thermal barrier coatings (TBCs) with aluminide bond coats is strongly influenced by bond c oat oxidation behavior. This study investigated oxide (Al2O3) formation dur ing EB-PVD processing of TBCs with (NiPt)Al bond coats. The effects of subs trate composition, coating impurities and bond-coat grit-blasting on the ox ide phases, residual stress and microstructure were evaluated. As-deposited , high-purity commercial bond coats contained high concentrations of sulfur and other impurities at their surfaces. Numerous small voids formed at the oxide-metal interface when as-deposited bond coats were oxidized during EB -PVD processing. Grit-blasting of (Ni,Pt)AI had a significant impact, since the formation of alpha -Al2O3 during EB-PVD processing was significantly e nhanced and voids did not form beneath the scale. Preliminary cyclic oxidat ion testing suggested an influence of superalloy sulfur content on TBC dura bility. (C) 2001 Elsevier Science B.V. All rights reserved.