The isothermal steam oxidation behavior of Cr-coated Zr-1Nb alloy at 1350 ℃ and 1400 ℃ was investigated. The temperatures are above the Cr-Zr eutectic temperature. The reliability of the experimental setup and methodology was confirmed by conducting isothermal steam oxidation experiments on bare Zr-1Nb specimens at 1100∼1400 ℃, and the corresponding oxidation kinetics correlation was obtained. After the eutectic-oxidation reaction, the surface of the coated specimens exhibited a “crocodile skin” morphology composed of “ridges” and “hollows”, which was attributed to the non-uniform eutectic reaction. Due to the much higher O affinity of Zr compared to Cr, and the higher solubility of Cr in β-Zr compared to α-Zr(O) and ZrO, the ZrO and α-Zr(O) layers initially grew on the Cr-Zr eutectic during oxidation. Cr continuously diffused inward and eventually precipitated as Cr-rich phases within the metallic matrix. Three types of Cr-rich phases were observed, with varying oxygen content and reflecting the oxidation process of the Cr-rich phases. The Cr-rich phases were ultimately oxidized into a mixture of CrO and ZrO. The parabolic weight gain rates for the oxidation of Cr-Zr eutectic are compared with the oxidation kinetics correlation derived from the bare Zr-1Nb specimens, and the model applicability of the oxidation kinetics correlations of Zr alloys in the simulations of Cr-Zr eutectic-oxidation reaction is discussed.

中文翻译：

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高温蒸汽环境下Cr-Zr系共晶氧化偶联反应研究

研究了镀铬Zr-1Nb合金在1350 ℃和1400 ℃下的等温蒸汽氧化行为。温度高于 Cr-Zr 共晶温度。通过在1100∼1400 ℃下对裸Zr-1Nb样品进行等温蒸汽氧化实验，证实了实验装置和方法的可靠性，并得到了相应的氧化动力学关系式。共晶氧化反应后，涂层试样表面呈现出由“脊”和“凹”组成的“鳄鱼皮”形貌，这是由于不均匀的共晶反应造成的。由于 Zr 与 Cr 相比具有更高的 O 亲和力，并且与 α-Zr(O) 和 ZrO 相比，Cr 在 β-Zr 中的溶解度更高，因此 ZrO 和 α-Zr(O) 层最初在 Cr- 上生长。氧化过程中Zr共晶。 Cr不断向内扩散，最终在金属基体中以富Cr相的形式析出。观察到三种类型的富铬相，它们具有不同的氧含量，反映了富铬相的氧化过程。富Cr相最终被氧化成CrO和ZrO的混合物。将 Cr-Zr 共晶氧化的抛物线增重率与裸 Zr-1Nb 样品的氧化动力学相关式进行比较，以及 Zr 合金氧化动力学相关式在 Cr-Zr 共晶模拟中的模型适用性。讨论了氧化反应。