γ'+ β Binary-phase Ni-Al coatings were prepared on second-generation single-crystal superalloy René N5 (N5) substrates by electron beam physical vapor deposition.Inter-diffusion behavior between coatings and substrates at 1100 ℃ and its effects on microstructure stability of the substrates were investigated.A 3-μm-thick substrate diffusion zone (SDZ) layer forms beneath the coating/substrate interface after 5-h heat treatment.The SDZ layer is composed of γ'-Ni3Al phases and needle-like precipitates growing along (100) or (100) direction.After 100-h annealing,the thickness of the SDZ layer increases to ～ 17 μm,much lower than that of the single β-NiAl-coated substrate,while keeping single-crystal microstructure.