Effects of the constitution of CrON diffusion barrier on the oxidation resistance and interfacial fracture of duplex coating system

The duplex coating system of a NiCrAlY overlayer with a CrON diffusion barrier with different phase contents was deposited by AIP method. The duplex coatings were characterized regarding their microstructure, and the ability of the diffusion barrier was evaluated. The oxidation resistance and the interfacial strength of the duplex coatings were investigated. The results indicated that the duplex coating system with a diffusion barrier with an O/N ratio ∼66 and a lower Cr2O3 phase content exhibited more excellent oxidation resistance and lesser interdiffusion than with a diffusion barrier with O/N ∼30.1. The exposed coating samples possessed an improved interfacial strength compared with the annealed samples in the two duplex coating systems. The stronger interfacial strength in the coating system with a diffusion barrier with a low Cr2O3 phase content was related to the fewer defects and lower residual stress in the diffusion barrier.

► The microstructures in the diffusion barrier are strongly influenced by the Cr2O3/CrN ratio.
► The CrO50N diffusion barrier with a low Cr2O3 content exhibits excellent barrier ability.
► The oxidation-resistance of the NiCrAlY overlayer mainly depends on Al level in the coating.
► The interfacial strength is related with the defect density and interfacial residual stress in the diffusion barrier.