Oxidation and interfacial fracture behaviour of NiCrAlY/Al2O3 coatings on an orthorhombic-Ti2AlNb alloy

Al2O3 diffusion barriers of various thicknesses have been fabricated by filtered arc ion plating between the NiCrAlY coating and the O-Ti2AlNb alloy. Isothermal oxidation tests and three-point bend tests have been conducted to investigate the influence of the Al2O3 diffusion barriers on the oxidation and interfacial fracture behaviour of the coatings. The results indicate that the Al2O3 diffusion barrier defers interdiffusion and gives oxidation resistance of the NiCrAlY coatings. The thickness of the Al2O3 interlayer not only influences the oxidation behaviour but also affects the interfacial fracture properties. Additionally, thermal exposure affects the critical load in three-point bend tests.

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► Interdiffusion between the NiCrAlY coating and Ti2AlNb substrate was very serious.
► Al2O3 diffusion barriers deferred interdiffusion and interfacial reaction obviously.
► Diffusion barriers affected the mechanical properties and interfacial strength.
► Diffusion barriers influenced the damage behaviour during three-point bend test.