【作者】 赵茹；

【导师】 宋诗哲；

【作者基本信息】 天津大学 ， 应用化学， 2009， 博士

【摘要】 在我国能源发展战略中,核能占有重要的地位。今后十几年内,我国要兴建大批大型的核电站,但核电设备的腐蚀问题始终是核电发展的重大课题。尤其是核电关键材料的应力腐蚀开裂问题,直接影响着核电站的服役寿命和人员安全。核电站关键材料应力腐蚀在线检测的研究工作,对于设备延寿,腐蚀损伤检修和材料安全性评估等均具有重要的意义。因此,本文主要针对不锈钢应力腐蚀的电化学检测开展研究。在实验室条件下建立了慢应变速率拉伸(SSRT)及恒载荷应力腐蚀电化学噪声测试系统,并与多种测试手段相结合,从测试方法确定、数据解析、电化学噪声方法适用性等方面开展了工作。应用零阻电流计(ZRA)模式电化学噪声方法(EN)研究了核电用超低碳控氮304NG及敏化304SS慢应变速率拉伸下的应力腐蚀过程,采用电流和电位时域谱、频域谱、小波分析等多种方法,初步得到了应力腐蚀过程的电化学电位与电流噪声的特征,探讨了应力腐蚀过程中Rn的变化,提出了定性判断应力腐蚀萌生与扩展阶段的依据。将恒载荷EN测试与声发射方法(AE)结合研究了敏化304SS应力腐蚀过程。得到应力腐蚀过程中膜形成、膜破裂与裂纹形成、裂纹扩展等过程的电化学噪声谱及相应的声发射信号特征,结果证实两种测试方法具有较好的一致性。采用EN方法研究了不同预制疲劳裂纹试样未加载与SSRT下的腐蚀行为,提出预制疲劳裂纹扩展的电化学噪声特征,并应用扫描Kelvin探针技术对于慢拉伸实验前后裂纹试样的表面形貌与表面电位分布进行分析。结果表明两种测试方法均可表征裂纹的扩展。运用电化学电位噪声方法研究了不锈钢管焊缝区在热浓碱中的腐蚀行为,结果表明:电位PSD谱线性部分斜率K值可判断不锈钢焊缝区是否发生局部腐蚀;出现局部腐蚀裂纹时,电位PSD曲线在高频处出现白噪声;可采用特征频率fn定性判断试样表面不同的腐蚀状态。研究了高温高压动态水环境中EN方法的适用性。得到0-3m/s流速下304NG噪声时域谱。结果表明,流速的增加对EN测试影响较小。电化学噪声技术可用于动态高温高压水环境中,并可实现对材料腐蚀敏感性的监检测。更多还原

【Abstract】 Nuclear Power Plant has played an important role in our national energy resource developmental strategies. Many Large Nuclear Power Stations will have been built in the past ten years. However, corrosion is still great problem of the nuclear industry affecting components especially Stress Corrosion Cracking (SCC). The corrosion of Stainless Steel (SS) which is especially used as structural materials will influence the Nuclear power plant active time and security directly. It is significant to study the corrosion behavior, timely detection and proper action would reduce the costs of damage, and in some cases even prevent the occurrence of disastrous events. Electrochemical corrosion occurred under force is the essential of SCC. In this paper, Stress Corrosion Cracking of stainless steel electrochemical technologies is studied.In this paper, on line detective methods based on EN technology about SCC under the SSRT and constant load were presented in lab. The testing mode, data analysis and the system used in the field were discussed.Electrochemical voltage and current noise were measured by ZRA simultaneously during stress corrosion cracking (SCC) process of 304NG and sensitized 304SS in SSRT test. In order to characterize the SCC processes of austenitic stainless steel, Visual records and time analysis of the current and potential data along with the spectral estimation using FFT method and Wavelet analysis gave useful information on these corrosion processes. It obtained the curve of Rn. Moreover, EN potential and current spectrum characteristics were preliminary mastered and obtained the judgment to distinguish SCC generation from development.Acoustic emission (AE) technique and EN were used simultaneously to study the process of SCC on sensitized 304SS. There are at lease four stage of SCC which were the films formed, film rupture and SCC Initiation and propagation process. The analysis of the AE signals in conjunction with EN showed the two testing techniques had good consistency to detection of SCC.The corrosion behaviors of fatigue pre-cracking 304SS with and without stress were detected by means of EN measurements in different solution. The EN characteristics of cracking propagation were obtained. Moreover, the characteristics of surface morphology image and Volta potential distribution over the surface has been studied before and after experiment with Kelvin probe. The results showed that Kelvin and EN could get the same judgment that its cracking propagated.Use of electrochemical potential noise to detect corrosion behavior of the weld zone of 304SS in the heat concentrate lye, and analyzed its parameter. The high frequency roll-of slop K in the PSD plot could detect whether the localized corrosion occurred or not. When localized corrosion cracking initiation, amplitude was large and termination appeared, a high frequency plateau appeared in the power spectrum by use of the Fast Fourier Transform (FFT). Moreover, the different state of specimens had been distinguished by fn the frequency of events.Autoclave test system had been used to study the applicability of EN at high temperature and pressure with dynamic water system. Using the same electrodes measured by ZRA obtain the current and potential electrochemical noise in time domain. The results showed EN could be used to detect local corrosion sensitivity evaluation at high temperature and pressure with dynamic water system.更多还原