摘要：Recently, amorphous Hf-B-Si-C-N coatings found to demonstrate superior high-temperature oxidation resistance. The microstructure evolution of two coatings, Hf 7 B 23 Si 22 C 6 N 40 and Hf 6 B 21 Si 19 C 4 N 47 , annealed to 1500 °C in air is investigated to understand their high oxidation resistance. The annealed coatings develop a two-layered structure comprising of the original as-deposited film followed by an oxidized layer. In both films, the oxidized layer possesses the same microstructure with HfO 2 nanoparticles dispersed in an amorphous SiO x -based matrix. The bottom layer in the Hf 6 B 21 Si 19 C 4 N 47 coating remains amorphous after annealing while Hf 7 B 23 Si 22 C 6 N 40 recrystallized partially showing a nanocrystalline structure of HfB 2 and HfN nanoparticles separated by h-Si 3 N 4 and h-BN boundaries. The HfB 2 and HfN nanostructures form a sandwich structure with a HfB 2 strip being atomically coherent to HfN skins via (111)-Hf monolayers. In spite of the different bottom layer structure, the oxidized/bottom layer interface of both films was found to exhibit a similar microstructure with a fine distribution of HfO 2 nanoparticles surrounded by SiO 2 quartz boundaries. The high-temperature oxidation resistance of both films is attributed to the particular evolving microstructure consisting of HfO 2 nanoparticles within a dense SiO x -based matrix and quartz SiO 2 in front of the oxidized/bottom layer interface acting as a barrier for oxygen and thermal diffusion.
