Oxidation Behavior of Ru-Containing Ni-Base Single-Crystal Superalloys
The 4th and advanced generation Ni-base single crystal superalloys, which contain large amounts of refractory metals for strengthening and platinum group metals, e.g., Ru, for TCP-phase prevention, show excellent high-temperature strengths. However, these alloying elements seem to decrease high-temperature oxidation resistance. In this study, Ni-base superalloys with various amounts of Ta, Re and Ru were examined in isothermal and cyclic exposures at 1373K to investigate the effect on the oxide growth rate and resistance to scale spallation. Structures of the oxide for the alloys were analyzed by XRD, SEM and EDX, and the oxidation kinetics is discussed. Ru and Re were found to degrade the oxidation resistance by the vaporization of their oxide. Ta-rich oxide in the spinel layer affects to stabilize ruthenium and rhenium oxide in the scale and improve the oxidation resistance of Ru-containing Ni-base superalloys.
Shigeji Taniguchi, Toshio Maruyama, Masayuki Yoshiba, Nobuo Otsuka and Yuuzou Kawahara
K. Kawagishi et al., "Oxidation Behavior of Ru-Containing Ni-Base Single-Crystal Superalloys", Materials Science Forum, Vols. 522-523, pp. 317-322, 2006