Ion-plated Al-Al2O3 films as diffusion barriers between NiCrAlY coating and orthorhombic-Ti2AlNb alloy

Ion-plated Al-Al2O3 cermet films were fabricated as diffusion barriers between NiCrAlY coating and orthhombic-Ti2AlNb alloy. The oxidation and interdiffusion behaviour of coatings with and without diffusion barrier were investigated in isothermal and cyclic oxidation tests at 800 degrees C. The results indicated that substantial interdiffusion and rapid oxidation degradation occurred in the coated specimens without diffusion barrier. With Al-Al2O3 diffusion barriers, deferred interdiffusion and improved oxidation resistance was observed. Among them, duplex coating containing 1Al-Al2O3 interlayer exhibited the best performance. Coefficient of diffusion hindering and factor of reaction hindering were proposed to compare and quantify the efficiency of the diffusion barriers. (C) 2010 Elsevier Ltd. All rights reserved.