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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% O 2-99% 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 Al 2 O 3 scale. Additionally, the outward diffusion of elements from Inconel 617 penetrated the unoxidized parts of the 800 • C-annealed Ru-Al multilayers.

Abstract:In this study, equiatomic Ru-Zr coatings were deposited on Si wafers at 400 • C by using direct current magnetron cosputtering. The plasma focused on the circular track of the substrate holder and the substrate holder rotated at speeds within 1-30 rpm, resulting in cyclical gradient concentration in the growth direction. The nanoindentation hardness levels of the as-deposited Ru-Zr coatings increased as the stacking periods of the cyclical gradient concentration decreased. After the coatings were annealed in a 1% O 2 -99% Ar atmosphere at 600 • C for 30 min, the internally oxidized coatings shifted their respective structures to a laminated structure, misaligned laminated structure, and nanocomposite, depending on their stacking periods. The effects of the stacking period of the cyclical gradient concentration on the mechanical properties and structural evolution of the annealed Ru-Zr coatings were investigated in this study.