摘要
为探究表面机加工对核电用奥氏体不锈钢应力腐蚀开裂(SCC)行为的影响,考察了304L和316L两种不锈钢在300℃高温高压水中的氧化行为,并采用电化学方法对氧化膜的腐蚀性能进行评估,同时利用U弯样品法研究了其在高温高压水环境下的SCC,分析了表面机加工对SCC的影响。结果显示:随着氧化时间的延长,样品表面的氧化物颗粒不断增加,浸泡80 d后,两种材料的氧化膜厚度可达到微米级;随着浸泡时间的延长,两种不锈钢的抛光和机加工样品表面氧化膜的耐蚀性均有所增强,但机加工样品的氧化膜耐蚀性劣于抛光样品。在300℃高温水环境下浸泡365 d后,仅部分304L不锈钢机加工样品萌生应力腐蚀裂纹;在含500 mg/L氯离子的环境下,浸泡100 d后两种不锈钢机加工样品在变质层处开始萌生裂纹,浸泡365 d后,萌生的应力腐蚀裂纹数量和长度均显著增加。无论是否添加氯离子,浸泡365 d后所有抛光样品均未萌生应力腐蚀裂纹。可知,表面机加工一方面增加了不锈钢表面的残余应力水平,另一方面破坏了样品表面的微观结构,形成了变质层,导致高温水环境下形成的氧化膜保护性降低,共同导致了应力腐蚀裂纹的萌生。氯离子对应力腐蚀开裂的裂纹萌生和扩展均有显著的促进作用,在氯离子含量为500 mg/L的高温高压水环境下裂纹扩展速率增加约15倍。
To investigate the effect of surface machining on the SCC behavior of austenitic SS used in nuclear power plants,this paper focuses on the study of the oxidation behavior of two types of 304L and 316L SSs in 300 C high temperature water,and evaluates the corrosion resistance of the oxide film using electrochemical methods.SCC tests were conducted on both types of SSs using U-bend samples in high temperature water environment.The influence of surface machining on SCC was analyzed.The results show that the oxide particles on the surface of the SS samples continusly grew as the oxidation time increased.After 80 days of immersion,the thickness of the oxide film on both materials reached the micron level.With prolonged immersion,the corrosion resistance of both polished and machined samples of the two SSs improved,while the corrosion resistance of the oxide film on the machined samples were inferior to those of the polished samples.After immersion in 300 C high-temperature water environment for 365 days,only some machined samples of 304L SS initiated SCC cracks.In an environment containing 500 mg/L chloride ions,cracks began to initiate at the deformation layer of the machined samples for both SSs after 100 days of immersion.Both the number and length of cracks increased significantly after 365 days of immersion.No SCC cracks were observed in any of the polished samples after 365 days of immersion regardless of the presence of chloride ions.Analysis of the experimental results indicates that surface machining increases the residual stress levels on the stainless steel surfaces while also disrupting the microstructure,leading to the formation of an altered layer.This results in a reduced protective capability of the oxide film formed in the high-temperature water environment,contributing to the initiation of SCC cracks.Chloride ions significantly promoting promote both the initiation and propagation of SCC cracks;in a high-temperature,high-pressure water environment with a chloride ions concentration of 500 mg/L,the crack propagation rate increased by approximately 15 times in the present study.
作者
武焕春
刘向兵
徐超亮
全琪炜
李远飞
董海涛
安英辉
姜冠男
WU Huanchun;LIU Xiangbing;XU Chaoliang;QUAN Qiwei;LI Yuanfei;DONG Haitao;AN Yinghui;JIANG Guannan(Suzhou Nuclear Power Research Institute,Suzhou 215004,China;National Engineering Research Center for Nuclear Power Plant Safety&Reliability,Suzhou 215004,China;Beijing Advanced Innovation Center for Materials Genome Engineering,Institute of Advanced Materials and Technology,University of Science and Technology Beijing,Beijing 100083,China;Daya Bay Nuclear Power Operations And Management Co.,Ltd.,Shenzhen 518000,China)
出处
《材料科学与工艺》
北大核心
2025年第6期50-59,共10页
Materials Science and Technology
基金
国家自然科学基金青年基金资助项目(52101066)
广东省基础与应用基础研究重大项目(2019B030302011)。
关键词
表面机加工
奥氏体不锈钢
核电主管道
氧化膜
应力腐蚀开裂
电化学
高温高压水
氯离子
surface machining
austenitic stainless steels
nuclear power main pipeline
oxide film
stress corrosion cracking
electrochemical
high-temperature and high-pressure water
chloride ion
