硫酸盐还原菌作用下2205双相不锈钢在3.5%NaCl溶液中应力腐蚀开裂行为研究

采用动电位极化技术、慢应变速率拉伸实验(SSRT)以及扫描电子显微镜(SEM)等方法研究了硫酸盐还原菌(SRB)新陈代谢对2205双相不锈钢(DSS)在3.5%(质量分数)NaCl溶液中的应力腐蚀开裂(SCC)行为的影响。结果表明,与无菌溶液中相比,SRB的存在促进了2205DSS的阳极溶解过程,诱发了点蚀,为SCC萌生提供了裂纹源。2205DSS的SCC敏感性与SRB活性浓度呈正相关,在稳定生长期SRB活性浓度最大,此时2205DSS的SCC敏感性最大。2205DSS在含SRB的3.5%NaCl溶液中发生的SCC机理为阳极溶解和氢脆混合控制机制。SRB作用下,2205DSS中铁素体相表现为穿晶解理特征,奥氏体相表现为韧性撕裂的特征,铁素体相具有更高的SCC敏感性。

Stress Corrosion Cracking Behavior of 2205 Duplex Stainless Steel in 3.5%NaCl Solution with Sulfate Reducing Bacteria

Materials served in marine environments are not only subjected to the Cl-and ocean currents,but also suffered from biological fouling.The effect of sulfate reduction bacteria(SRB)metabolism on the stress corrosion cracking(SCC)behavior of 2205 duplex stainless steel(DSS)in 3.5%(mass fraction)NaCl solution were investigated by means of potentiondynamic polarization technology,slow strain rate test(SSRT)and scanning electron microscopy(SEM).The results showed that compared with the sterile solution,the presence of SRB promoted the anodic dissolution process of 2205 DSS in the bacterial solution and induced pitting,which facilitated cracks initiation.The SCC sensitivity of 2205 DSS was positively correlated with the concentration of SRB activity.The SRB activity concentration was the highest during their stable growth period,and the resulted metabolite H2S could induce the increase of brittleness of the steel.In this case,SCC sensitivity of 2205DSS was the highest.The SCC mechanism of 2205DSS in 3.5%NaCl solution containing SRB was the mutual control of anodic dissolution and hydrogen damage.In the presence of SRB,the ferritic phase in 2205DSS exhibited transgranular cleavage,while the austenitic phase exhibited ductile tearing,and the ferritic phase had higher SCC sensitivity.