304不锈钢应力腐蚀行为研究

Study on Stress Corrosion Behavior of 304 Stainless Steel

本文进行慢应变速率应力腐蚀试验附以不同浓度氯离子水雾腐蚀介质,采用金相显微镜、扫描电镜(SEM)和扫描探针显微镜(AFM)对试样组织微观形态进行观察分析。对应变诱发马氏体相变机理及氯离子对奥氏体不锈钢耐蚀性的影响进行探讨,研究结果表明不锈钢中奥氏体处于亚稳态,一定量变形将诱导马氏体相变,且变形量越大,马氏体相越多。在10%以内变形,奥氏体晶界比晶粒内部变形更大。马氏体优先在晶界处形核长大。随着应变增大,晶粒内部也产生马氏体。奥氏体不锈钢在应力存在条件下,对含氯离子的氯化钠腐蚀介质敏感。氯离子破坏不锈钢钝化膜,使腐蚀加重,氯离子浓度越高,腐蚀越严重。

In this paper,the slow strain rate stress corrosion test was carried out with water mist corrosion medium with different concentrations of chloride ions.The microstructure of the sample was observed and analyzed by metallographic microscope,scanning electron microscope(SEM)and scanning probe microscope(AFM).The mechanism of strain-induced martensitic transformation and the effect of chloride ions on corrosion resistance of austenitic stainless steel were discussed.The results show that austenite in stainless steel is in metastable state,and a certain amount of deformation will induce martensitic transformation,and the larger the deformation,the more martensite.Within 10%of deformation,the deformation of austenite grain boundary is larger than grain internal deformation.Martensite was preferred to nucleate and grow at grain boundaries.With the increase of strain,martensite is also produced in the grains.Austenitic stainless steel is sensitive to Chloride corrosive medium containing chloride ions in the presence of stress.Chloride ion damages the passivation film of stainless steel,aggravating the corrosion.The corrosion of chlorine ion concentration is higher,the more serious.