Deposition, characterization and high-temperature steam oxidation behavior of single-phase Ti2AlC-coated Zircaloy-4

Oxidation of single-phase and dense Ti2AlC coatings with or without a 500 nm TiC diffusion barrier deposited on Zircaloy-4 by annealing of nanoscale multilayer stacks between 800 °C and 1200 °C in high-temperature steam was investigated. Coatings without TiC barrier formed a duplex scale: outer θ-Al2O3 rich layer mixed with TiO2 and inner porous TiO2 layer; correspondingly, a triple-layered scale (θ-Al2O3 + TiO2/θ-Al2O3/TiO2) grew on coatings with barrier at 800 °C. The TiC barrier suppresses the rapid diffusion of Al into the substrate, contributing to improved performance and longer life of Ti2AlC/TiC coatings. However, both coatings demonstrated low protection effect from 1000 °C in steam.