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 coat oxidation behavior. This study investigated oxide (Al2O3) formation during EB-PVD processing of TBCs with (Ni,Pt)Al bond coats. The effects of substrate composition, coating impurities and bond-coat grit-blasting on the oxide 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)Al had a significant impact, since the formation of α-Al2O3 during EB-PVD processing was significantly enhanced and voids did not form beneath the scale. Preliminary cyclic oxidation testing suggested an influence of superalloy sulfur content on TBC durability.