690合金在饱和氧水环境中的腐蚀疲劳裂纹扩展行为研究

发布时间：2017-12-28 04:25

本文关键词：690合金在饱和氧水环境中的腐蚀疲劳裂纹扩展行为研究　出处：《西华大学》2015年硕士论文　论文类型：学位论文

【摘要】：690合金因具有优异的高温力学性能和抗腐蚀性能,广泛用于压水堆蒸汽发生器传热管。核电运行经验表明,690合金在反应堆工况条件下具有腐蚀疲劳破坏倾向,有必要对其腐蚀疲劳性能进行研究。本文采用紧凑拉伸试样,在保证裂纹尖端处于小范围屈服状态下,研究了饱和氧浓度条件下国产690合金在模拟压水堆一回路水环境中和高温高纯水环境中的腐蚀疲劳裂纹扩展行为,得到以下结论：(1)疲劳裂纹扩展速率由裂纹尖端塑性区、载荷频率及服役环境联合决定。裂纹尖端处于小范围屈服时,裂纹尖端发生显著的塑性变形,在腐蚀环境和循环载荷的作用下这些区域快速溶解,促进裂纹加速扩展。在腐蚀环境中,载荷频率同样对裂纹扩展速率产生显著影响。(2)裂纹扩展路径均为穿晶型,扩展过程中出现的分支和偏折现象都将导致裂纹扩展速率的降低,从而影响环境影响因子(F。n)的计算值。断口具有明显的腐蚀疲劳特征,由山脊区、疲劳平台和微裂纹组成；裂纹在三维空间中扩展,部分区域可以观察到氧化物的存在。(3)缺口表面疲劳裂纹扩展研究及预制裂纹样品裂纹扩展研究均表明,交变载荷作用下,裂纹尖端形成多个裂纹核心并同时扩展,与载荷垂直方向一致性较好的裂纹快速扩展发展为主裂纹,其余扩展缓慢成为所观察到的支裂纹。(4)统计分析结果显示,引入F。。作为表征参数可以有效地减少材料不均匀性及仪器测量误差对实验结果带来的不利影响。饱和氧模拟一回路水环境促进裂纹扩展速率提高可达5倍,在饱和氧高温高纯水中可以达到4倍。
[Abstract]:690 alloy is widely used in the steam generator heat transfer tube of PWR because of its excellent mechanical properties and corrosion resistance. The operation experience of nuclear power shows that 690 alloy has the tendency of corrosion fatigue failure under the condition of reactor, and it is necessary to study its corrosion fatigue performance. This paper adopts compact tensile specimen, the crack tip in the small scale yielding condition, the corrosion fatigue crack propagation behavior of saturated oxygen concentration under the condition of domestic 690 alloy water pressure in simulated pile loop water environment and high temperature water environment, get the following conclusions: (1) the fatigue crack growth rate by crack tip area, load frequency and service environment of joint decisions. When the crack tip is in a small area, there will be significant plastic deformation at the crack tip. These regions will be dissolved rapidly under the corrosive environment and cyclic loading, which will accelerate the crack propagation. In the corrosive environment, the load frequency also has a significant effect on the crack growth rate. (2) the crack propagation paths are all transgranular. The branching and deflections in the process of expansion will lead to the decrease of the crack growth rate, thereby affecting the environmental impact factor (F). The calculated value of n). The fracture surface has obvious corrosion fatigue characteristics, which is composed of ridge area, fatigue platform and micro crack. Cracks expand in three-dimensional space, and the existence of oxides can be observed in some areas. (3) the gap surface fatigue crack growth and crack propagation of prefabricated crack samples show that the alternating loads, the crack tip and the core to form a plurality of crack expansion, better crack and vertical load consistency of the rapid expansion of the development of the main crack, the slow expansion of more than a crack observed. (4) the results of statistical analysis show that the F is introduced. As a characterization parameter, the inhomogeneity of the material and the negative effect of the instrument measurement error on the experimental results can be effectively reduced. The simulation of the first loop water environment by saturated oxygen can increase the rate of crack growth by up to 5 times, and can reach 4 times in saturated oxygen high temperature and high pure water.
【学位授予单位】：西华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG131

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