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Abstract：
An accurate evaluation of stress corrosion cracking (SCC) in 13Cr martensitic stainless steel (MSS) is still missing due to the lack of an in-situ insight into the process evolution and full characterization of the corrosion morphology. In this work, two main regimes involved in the SCC progression, including localized corrosion and cracking, were comparatively studied using in-situ acoustic emission (AE) monitoring and three-dimensional (3D) X-ray computed tomography (XCT) scanning. The stress corrosion tests were conducted with u-bent smooth specimens subjected to a single droplet of 1 μL 1% neutral NaCl solution. Localized corrosion and cracking evolution were controlled in tempered and quenched steel specimens, respectively. From XCT scanning, localized corrosion was featured by an irregular corrosion pit with deposited corrosion products containing cracks. The single dominant SCC crack was observed to initiate from corrosion pit and propagate with a 3D tortuous and discontinuous morphology. AE signals were detected in both cases. Correlated with in-situ observations and clustering analysis, source identification of AE signals was proposed. AE signals during localized corrosion were assessed to be mainly from cracking within the deposited corrosion products. Comparatively, hydrogen-bubble evolution, plastic deformation, and crack-branches coalescence were proposed as the AE sources of cracking evolution.
摘要：
由于缺乏对过程演变和腐蚀形态的全面表征的原位洞察，对13Cr马氏体不锈钢（MSS）中的应力腐蚀开裂（SCC）的准确评估仍然缺失。在这项工作中,涉及SCC进展的两个主要制度，包括局部腐蚀和开裂，使用原位声发射（AE）监测和三维（3D）X射线计算机断层扫描（XCT）扫描进行了比较研究。应力腐蚀测试是用U形弯曲的光滑试样进行的，该试样经受了1μL1％中性NaCl溶液的单个液滴。在回火和淬火钢试样中控制了局部腐蚀和开裂演变，分别。从XCT扫描，局部腐蚀的特征是不规则的腐蚀坑，沉积的腐蚀产物含有裂纹。观察到单个占主导地位的SCC裂纹从腐蚀坑开始，并以3D曲折和不连续的形态扩展。在两种情况下均检测到AE信号。与现场观测和聚类分析相关，提出了AE信号的来源识别。局部腐蚀期间的AE信号被评估为主要来自沉积的腐蚀产物内的开裂。相对而言,氢气气泡的演变，塑性变形,裂纹分支聚结被认为是裂纹演化的AE源。
