Zr-Sn系合金在过热蒸气中的腐蚀吸氢行为

研究第二相大小和种类对Zr-2和Zr-4合金在400℃,10.3MPa过热蒸气中腐蚀吸氢行为的影响。结果表明:吸氢量的多少和耐腐蚀性能的好坏之间并不一定存在严格的对应关系,而是与第二相大小和种类密切相关。在相同腐蚀增重下,含粗大第二相样品的吸氢量均大于含细小第二相样品;第二相比较粗大的Zr-2样品的吸氢量比Zr-4样品大得多;而第二相比较细小的Zr-2和Zr-4样品的吸氢量差别却很小。对Zr(Fe,Cr)2和Zr2(Fe,Ni)金属间化合物及纯锆进行的PCT和吸放氢动力学测试表明,前两者可自由吸放氢,且吸放氢速度快,而纯锆只能吸氢难以放氢。据此,Zr-Sn系合金在400℃,10.3MPa过热蒸气中腐蚀吸氢行为可以用提出的"在金属/氧化膜界面处Zr和OH-反应生成的氢可以优先被镶嵌在金属/氧化膜界面处的可逆吸放氢能力强于Zr的Zr(Fe,Cr)2和Zr2(Fe,Ni)第二相捕获,它们可作为吸氢的优先通道"的吸氢模型得到合理解释。

Hydrogen Absorption Behavior of Zircaloy Corroded in Super-Heated Steam

The hydrogen uptake behavior of Zircaloy-2 and Zircaloy-4 containing different second phase particles (SPPs) in size and category during corrosion test in super-heated steam at 400 oC/10.3 MPa was investigated. The amount of hydrogen uptake was not always corresponding to the corrosion resistance, while it was closely related to the SPPs size and category. At the same mass gain, the difference is significant in the amount of hydrogen uptake between the Zircaloy-2 and Zircaloy-4 specimens with coarse SPPs, while the difference is negligible in the amount of hydrogen uptake between the Zircaloy-2 specimens SPPs and Zircaloy-4 specimens with fine SPPs. The contribution of SPPs category to the hydrogen uptake is more notable to the specimens with coarse SPPs than specimens with fine SPPs. The tests, containing absorption pressure-composition-temperature (PCT), absorption and desorption kinetics, were proceeded in zirconium, Zr(Fe,Cr)2 and Zr2(Fe,Ni) intermetallic specimens. Results indicate that Zr(Fe,Cr)2 and Zr2(Fe,Ni) specimens could absorb and desorb hydrogen easily with high speed, while zirconium could only absorb hydrogen easily but desorb hydrogen difficultly. Based on these results, the hydrogen uptake behavior of Zircaloy corroded in super-heated steam at 400 oC /10.3 MPa were successfully explained with the model that the hydrogen generating from the reaction of zirconium and OH- at metal/oxide film interface can be captured by Zr(Fe,Cr)2 and Zr2(Fe,Ni) SPPs embedding at the metal/oxide interface. These SPPs with higher reversible absorbing and desorbing ability acted as a preferred path for hydrogen uptake.