Yttria partially stabilised zirconia as diffusion barrier between NiCrAlY and Ni-base single crystal René N5 superalloy

• An yttria partially stabilised zirconia layer was fabricated as diffusion barrier.
• Diffusion barrier suppressed the interdiffusion of alloying elements at 1100 °C.
• Diffusion barrier improved the oxidation resistance of NiCrAlY coating system.

A 7–8 wt.% yttria partially stabilised zirconia (YSZ) layer was fabricated by electron beam physical vapour deposition as a diffusion barrier (DB) between NiCrAlY coating and Ni-base single crystal René N5 superalloy. Oxidation and interdiffusion behaviour of the coating system was investigated at 1100 °C. The YSZ interlayer, as an active DB, reacted with Al from superalloy substrate and NiCrAlY overlayer to form two continuous adherent alumina layers, which suppressed interdiffusion between substrate and overlayer effectively. The results indicated that the coating system with DB exhibited excellent oxidation resistance due to the inhibition of interdiffusion of alloying elements.