An AIN interlayer was fabricated by filtered vacuum arc evaporation as a diffusion barrier (DB) between Ni + CrAlYSiHfN composite coating and K417G superalloy. Microstructure changes of the AIN DB were investigated after exposure at 1000 and 1100 degrees C. Amorphous structure was found in the as-deposited AIN DB, which went through crystallization when exposing at high temperature. The AIN DB suppressed interdiffusion between overlayer and substrate effectively after 200 h exposure at both 1000 degrees C and 1100 degrees C. A few substrate element precipitates were observed within the grain boundary of the AIN DB after exposure at 1100 degrees C for 200 h. (C) 2015 Elsevier B.V. All rights reserved.