Thermal Stability of Ru–Al Multilayered Thin Films on Inconel 617

Ru-riched and equiatomic Ru–Al multilayered thin films were fabricated on Si and Inconel 617 substrates. These thin films exhibited a multilayered structure that is caused by stacking cyclical gradient concentration through cosputtering. X-ray diffraction analysis indicated that the as-deposited Ru–Al multilayers comprised Ru and RuAl phases. Oxidation that is caused by annealing atmospheres and elements diffused from substrates was investigated. The results indicated that the inward diffusion of O at 600 °C in a 1% O2–99% Ar atmosphere was restricted by the formation of an amorphous Al-oxide sublayer, and inward diffusion of O at 800 °C in air was limited by the formation of a crystalline Al2O3 scale. Additionally, the outward diffusion of elements from Inconel 617 penetrated the unoxidized parts of the 800 °C–annealed Ru–Al multilayers.