Failure mechanism and interfacial diffusion behavior of Ru-doped NiAlHf coatings at 1200 °C

Ru-doped NiAlHf coatings were deposited on Ni-based single crystal substrate by arc ion plating technology. The failure mechanism and interfacial diffusion behavior were comparatively investigated with NiAlHf coating using scanning electron microscopy, electron probe micro-analyzer, and transmission electron microscopy. The results indicated that microstructure evolution of oxide scale induced by element diffusion process significantly affected oxidation resistance of NiAlHf/Ru coatings, resulting in formation of cracks and voids, thereby accelerating failure process. The precipitates in interdiffusion zone and secondary reaction zone of the substrate initiated by interfacial element diffusion were P phase and σ phase, respectively. And the discrepancy in content was elucidated from the perspective of thermodynamics and kinetics. Besides, microstructural evolution between NiAlHf/Ru coatings and substrate was also deliberated. The research could not only provide profound understanding of NiAlHf/Ru coatings failure mechanism, but also had significant guidance for suppressing precipitation of topological close-packed phases and facilitating development of single crystal Ni-based superalloys.