Abstract Cr coatings have been deposited on the outer surface of zircaloy-4 tube with well control of thickness variations along the tube axis. A series of samples have been oxidized in high temperature steam environment at 1200 °C for different durations. Cr2O3 layers are formed on the surface of the Cr coatings after high temperature oxidation, however, we have found that the thickness of the Cr2O3 layers increases first, and then decreases. The reason is because the Cr2O3 is reduced by the zirconium substrate when the thickness of Cr2O3 reaches its maximum. More detailed study revealed that the entire process can be divided into three stages: initial oxidation stage (I); reduction stage (II); and the oxidation of the sub-coating zirconium at a lower rate than the uncoated Zry4 (III). In addition, precipitation of secondary phases both within the coatings and the zirconium substrate has been studied in detail which plays an important role during the oxidation process. Therefore, the oxidization behavior of the Cr-Zr system is more complex than generally assumed. This study has provided sufficient experimental evidences for the redox reaction between the Cr coating and Zry4 substrate. Diffusion channels of oxygen ions during the reduction reaction have also been studied systematically.

中文翻译：

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高温蒸汽环境下Zry4基体上Cr涂层氧化行为的系统研究

摘要 Cr 涂层已沉积在锆合金 4 管的外表面，并且沿管轴的厚度变化得到了很好的控制。一系列样品在 1200 °C 的高温蒸汽环境中氧化了不同的时间。高温氧化后在Cr涂层表面形成Cr2O3层，但我们发现Cr2O3层的厚度先增加后减小。原因是当Cr2O3 的厚度达到最大值时，Cr2O3 被锆基体还原。更详细的研究表明，整个过程可分为三个阶段：初始氧化阶段（I）；还原阶段（II）；和底涂层锆的氧化速率低于未涂层的 Zry4 (III)。此外，已经详细研究了涂层和锆基体中第二相的沉淀，这在氧化过程中起着重要作用。因此，Cr-Zr 系统的氧化行为比通常假设的更复杂。该研究为Cr涂层与Zry4基体之间的氧化还原反应提供了充分的实验证据。还系统地研究了还原反应过程中氧离子的扩散通道。