表面纳米化对X80管线钢应力腐蚀开裂行为的影响

Effect of surface nanocrystallization on stress corrosion cracking behaviors of X80 pipeline steel

通过超声表面滚压(ultrasonic surface rolling processing,USRP)方法对X80管线钢进行表面纳米化处理,利用金相显微镜和透射电镜对材料表面的微观组织进行了分析.采用慢应变速率拉伸试验(SSRT)和扫描电镜观察研究USRP对X80管线钢在NS4溶液中的应力腐蚀行为.结果表明,USRP处理使X80管线钢表层晶粒细化至纳米量级,X80管线钢随着外加电位的负移,断裂时间、断面收缩率、应变量都明显缩短,X80管线钢的SCC敏感性增加,应力腐蚀断口呈穿晶准解理特征,表面纳米化延长了X80管线钢的断裂时间,增加了应力腐蚀抗力.

Surface nanocrystallization of X80 pipeline steel was realized by ultrasonic surface rolling processing(USRP),and the microstructure of the steel surface was analyzed with optical microscope and transmission electron microscopy.The effects of USRP on the stress corrosion behavior of X80 pipeline steel in NS4 solution was investigated through the slow strain rate tensile tests(SSRT) and scanning electron microscopy.The results show that the USRP refined the grains in the X80 pipeline steel surface to nanometer level.With the negative shift of applied potential,the fracture time,section shrinkage and strain of the X80 pipeline steel significantly decreased,which suggested that the susceptibility to stress corrosion cracking(SCC) increased,and the fractured surface revealed transgranular with the feature of quasi-cleavage.Surface nanocrystallization could extend the fracture time and enhance the stress corrosion resistance of X80 pipeline steel.