NiAlHf coatings were deposited onto Ni-based single crystal (SC) superalloy with different crystal orientations by electron beam physical vapor deposition (EB-PVD). The effects of the crystal orientations of the superalloy substrate on inter-diffusion behavior between the substrate and the NiAlHf coating were investigated. Substrate diffusion zone (SDZ) containing needle-like p, phases and interdiffusion zone (IDZ) mainly consisting of the ellipsoidal and rod-like phases were formed in the SC alloy after heattreatment 10h at 1100 degrees C. The thickness of secondary reaction zone (SRZ) formed in the SC alloy with (011) crystal orientation is about 14 mu m after 50 h heat-treatment at 1100 degrees C, which is relatively thicker than that in the SC alloy with (001) crystal orientation, whereas the IDZ revealed similar thickness. (C) 2014 Elsevier B.V. All rights reserved.