Comparative degradation of nickel aluminized by slurry and by pack cementation under isothermal conditions

► Degradation mechanisms of a new TBC slurry system containing Al microspheres elucidated on pure nickel substrate. ► Greater oxidation kinetics of slurry compared to conventional pack coatings. ► Major role of the top coat of alumina hollow spheres to mass gains. ► Greater changes in composition and microstructure in slurry coatings than in pack. ► Delayed transformation of theta-alumina in pack compared to slurry coatings.