Ultra-high oxidation resistance of nano-structured thin films

Diffusion driven high-temperature oxidation is one of the most important failure mechanisms of protective thin films in industrial applications. Within this study, we investigated the diffusion of oxygen at 800 to 1100 degrees C through nano-laminated crystalline Ti-Al-N and amorphous Mo-Si-B based multilayer coatings. The most prominent oxygen diffusion pathways, and hence the weakest points for oxidation, were identified by combining O-18 tracer diffusion and atom probe tomography. An oxygen inward diffusion along column boundaries within Ti-Al-N layers in front of a visually prevalent oxidation front could be proven, highlighting the importance of these fast diffusion pathways. Furthermore, the amorphous Mo-Si-B layers act as barriers and therefore mitigate the migration of oxygen by accumulating reactive O species at a nanoscale range. Preventing oxygen diffusion along column boundaries - through the implementation of amorphous interlayers - lead to paralinear oxidation behavior and stable scales even after 7 hat 1100 degrees C. Our results provide a detailed insight on the importance of morphological features such as grain and column boundaries during high-temperature oxidation of protective thin films, in addition to their chemistry. (C) 2021 The Author(s). Published by Elsevier Ltd.

Automated summary

This study investigates the diffusion of oxygen at 800 to 1100 degrees C through nano-laminated crystalline Ti-Al-N and amorphous Mo-Si-B based multilayer coatings, revealing the importance of morphological features such as grain and column boundaries during high-temperature oxidation of protective thin films. The results show that preventing oxygen diffusion along column boundaries and implementing amorphous interlayers can lead to stable oxidation behavior even at 1100 degrees C.