Growth kinetics and microstructure characteristics of the Zr-Cr interlayer in a Cr-coated Zry-4 alloy exposed to high-temperature steam
Yahuan Zhao, Zhao Shen, Zhipeng Wang, Kun Zhang, Shixin Gao, Lu Wu, Xiaoqin Zeng
Abstract
The growth kinetics and microstructural characteristics of the interlayer in a Cr-coated Zry-4 alloy exposed to steam at 1200 °C for up to 10000 s were systematically studied through advanced characterization. A continuous ZrCr 2 Laves phase interlayer develops at the coating-substrate interface following a parabolic law . It transforms into a duplex structure composed of a ZrCr 2 layer and a thin Zr-Cr-O layer after a longer time of exposure. The growth of the interlayer is nearly terminated, and its thickness remains constant after oxidation for 3000 s. The prior interlayer transforms into the intertwined ZrO 2 and metallic Cr stringers after exposure to 10000 s due to the increased oxygen partial pressure inside the interlayer. The mechanisms controlling the formation and evolution of the interlayer are discussed.