<正> 一、引言 304不锈钢在核电工业中应用相当广泛,但该材料在高温高压水中的SCC倾向是一严重问题,对此已有不少研究和评述。近年来,对316型不锈钢在高温水中的SCC行为也进行了研究。普遍认为,不锈钢上氧化膜的稳定性及其破裂后的再钝化能力,是影响SCC裂纹萌生和扩展的一个重要因素;304钢在高温水中的SCC属于破膜和局部阳极溶解机理。但有关研究304钢SCC行为与其表面氧化膜的组成和结构之间关系的报道还不多。
The effects of temperature, chloride content and dissolved oxygen content on the susceptibility to stress corrosion cracking of type 304 stainless steel in high temperature water have been investigated. Both U bend and slow strain rate stress corrosion tests were performed,complemented by electrochemical polarization curve measurements and extensive oxide film analyses by Auger electron spectroscopy(AES). The U bend data showed decreasing susceptibility to cracking with increasing temperature, which correlated with thicker oxide films and greater enrichment of chromium in the films. In contrast,the slow strain rate tests indicated maximum susceptibility to cracking at 250℃ in the temperature range 200 to 300℃ and the susceptibility to cracking increased with increasing oxide thickness, The extent of chromium enhancements in the oxide layers was different for the two specimen types tested in equivalent environments. It is concluded that the best choice of test procedure for acquiring accelerated test data depnds upon the details of the application. U bend data will be more relevant for truly static load conditions that do not induce dynamic plastic strain, whereas slow strain rate data are more relevant for components that may experience plastic deformation during service.
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