Investigation on the microstructural evolution and oxidation resistance of Ru-doped NiAlHf coatings at 1200 °C

NiAlHf coatings with and without Ru-doping are deposited on Ni-based single crystal substrate by using arc ion plating (AIP) technology, of which microstructural evolution and oxidation resistance are comparatively investigated. The results reveal that oxide scale formed on NiAlHf coating surface has obvious ridge morphology and HfO2 is mainly distributed at grain boundaries. In contrast, the ridge structure of oxide scale on NiAlHfRu coating surface is not obvious and as-formed RuO2 is mainly distributed inside of grains. In addition, microstructure of oxide scale formed on both NiAlHf and NiAlHfRu coating surfaces is gradually evolved with increasing oxidation time, developing a rumpled surface. The formation of oxide composite, such as NiAl2O4 spinel and NiO, facilitates aggregation and growth of voids and cracks, accelerating premature failure of coating. Moreover, the growth stress and oxidation kinetics are also discussed to evaluate coating oxidation resistance properties. The purpose of research is to investigate microstructural evolution of NiAlHf coatings with assistance of reactive elements during oxidation process, which can contribute to improving oxidation resistance performance and service life of NiAlHf coating.