Microstructure and lifetime of Hf or Zr doped sputtered NiAlCr bond coat/7YSZ EB-PVD TBC systems

NiAlCr-X overlay coatings deposited by magnetron sputtering on IN100 and CMSX-4 superalloys and thereafter top-coated with 7YSZ thermal barrier coatings by EB-PVD were investigated with emphasis on the effects of superalloy type and Hf or Zr doping. The sputtered films in the “as coated” condition (after EB-PVD deposition) showed strong diffusion effects of different elements from the superalloys. The measured phase content of β and γ′ was in good agreement with calculated data obtained from experimental compositions normalized to a Ni-Al-Cr system following the guidelines of site preference of ternary alloying elements. Microstructure evolution and failure characteristics after furnace cyclic tests at 1100 °C were investigated as well. The lifetime of the coatings is equivalent to standard MCrAlY TBCs systems and is compared to PtAl and NiCoCrAlY coatings from literature. The effects of microstructure and elements diffusing from the substrates into the bond coat (Ti, Co, Mo and Ta) in combination with the effect of Hf- or Zr-doping is presented and discussed.