氯和氧对304N在高温水中应力腐蚀开裂的影响

摘要

采用慢应变速率拉伸试验(SSRT)与断口形貌分析技术研究304N不锈钢(固溶退火态)在300℃高温水中的应力腐蚀行为与机理.结果表明:304N在300℃高温水中的最大抗拉强度、延伸率以及断裂吸收能随Cl-浓度的增大显著降低；随氧浓度的急剧降低而显著增大；304N在高温水中发生应力腐蚀开裂(SCC)主要为穿晶型；随Cl-浓度增加,304N的应力腐蚀敏感性也迅速增加,在含50 mg/L Cl-的空气饱和高温水环境中,试样断口形貌表现为完全脆断；在溶解氧浓度急剧降低时,氯致应力腐蚀开裂的敏感性大幅降低,表明溶解氧对304N在高温水中的氯致应力腐蚀开裂具有明显的促进作用.%The stress corrosion cracking (SCO behavior and mechanism of solution-treated 304N stainless steel in high temperature water were studied by slow strain rate tensile test (SSRT) and fracture surface analysis. The results show that the SCC behavior of 304N in high temperature water reveals as transgranular cracking, and with the increasing of Cl- content, the susceptibility of SCC increases. The specimen shows brittle fracture mode when it is exposed to high temperature aerated water containing 50 mg/L Cl-. The present results also indicate that the susceptibility of chloride induced-SCC decreases significantly with decreasing of dissolved oxygen (DO) content in water, which reveals that DO plays a significant role in promoting SCC of 304N in high temperature water.