超临界水冷堆候选高温合金低周疲劳性能研究

Low-Cycle Fatigue Property of Candidate High Temperature Alloys for Supercritical Water Cooled Reactors

摘要:

采用MTS材料试验机研究了作为超临界水冷堆候选材料的Inconel-718、Incoloy-825、Incoloy-800H 3种高温合金，在650 ℃和室温、±0.5%应变幅的低周疲劳性能，并采用扫描电镜对试验后样品进行了断口分析。结果表明：在两种温度条件下，718的疲劳寿命均最高。温度对3种高温合金的稳态迟滞回线面积和弹性变形量几乎无影响；718的稳态迟滞回线面积远低于825和800H，而弹性变形量几乎达到825和800H的2倍，有利于提高其疲劳寿命。在循环变形过程中，718呈循环软化状态，825和800H呈先循环硬化再循环饱和状态，且在高温下循环硬化效应更明显。在650 ℃低周疲劳试验后，718样品断口表面的疲劳间距不足1 μm，而对于825和800H则分别达到2.28和2~20 μm，进一步表明了718在3种材料中低周疲劳性能最好。

Abstract:

Low cyclic fatigue (LCF) properties of three kinds of high temperature alloys (Inconel-718, Incoloy-825 and Incoloy-800H) as candidate materials for supercritical water cooled reactor (SCWR) were investigated at 650 oC and room temperature (RT) under a strain amplitude of ±0.5%, and fracture morphology of all the samples was observed by scanning electron microscope (SEM). The results show that the fatigue property of 718 is the best at both temperatures. The temperature has few effects on the area of hysteresis and elastic deformation for each alloy. The area of hysteresis for 718 is much lower than that of 825 and 800H, while the elastic deformation of 718 is as twice as that of other alloys, which is beneficial for improving the fatigue life. The 718 alloy shows a cyclic softening behavior in the testing; however, 825 and 800H coincide with the hardening-saturation mode; in addition, their cyclic hardening behavior is more obvious at 650 oC. SEM observation finds that the fatigue striation width after LCF testing at 650 oC is no more than 1 μm for 718, but up to 2.28 μm and 2~20 μm for 825 and 800H, respectively, which further demonstrates that 718 has the best fatigue property at 650 oC.