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MCrAlY can serve as stand-alone overlay coatings or bond coats in thermal barrier coating systems, and
its properties play a vital role in determining the performance of these coating systems. In order to further
understand the behavior of MCrAlY coatings, several NiCoCrAlY model alloys with di®erent levels of Re
(0.3 wt%, 6 wt%, and 9 wt%) were investigated. Microstructural observation showed the addition of Re
promoted the precipitation of Cr-rich phases, such as ®-Cr and ¾. The presence of ®-Cr lowered the coe±cient
of thermal expansion (CTE) of the coating alloys, which could reduce the CTE mismatch at the scale-metal
interface. The solid solution strengthening e®ect of Re is responsible for an increase in Rockwell hardness of
the coating alloys. But the isothermal oxidation resistance at 1100oC was deteriorated due to the precipitation
of brittle ®-Cr phase, a phase of inferior oxidation resistance compared with ¯-NiAl and °-Ni.