同成分的超细贝氏体钢和Q&P钢在海水中应力腐蚀开裂行为对比研究  

Comparative Study on Stress Corrosion Cracking Behavior of Ultrafine Bainitic Steel and Q&P Steel with Same Composition in Seawater

作　　者：苏志诚 张弦 程焱 刘静[1] 吴开明[1] SU Zhicheng;ZHANG Xian;CHENG Yan;LIU Jing;WU Kaiming(Hubei Province Key Laboratory of Systems Science in Metallurgical Process,State Key Laboratory of Refractory Material and Metallurgy,Collaborative Innovation Center for Advanced Steels,Wuhan University of Science and Technology,Wuhan 430081,China)

机构地区：[1]武汉科技大学、冶金工业过程系统科学湖北省重点实验室、耐火材料与冶金省部共建国家重点实验室高性能钢铁材料及其应用省部共建协同创新中心,武汉430081

出　　处：《中国腐蚀与防护学报》2024年第6期1495-1506,共12页Journal of Chinese Society For Corrosion and Protection

基　　金：武汉市科学技术局知识创新专项(20220108101020316);广东省基础与应用基础研究基金(2023A1515011154)。

摘　　要：采用显微表征方法(SEM、XRD、EBSD),电化学测试和慢应变速率应力腐蚀实验,研究了两种不同热处理工艺的先进高强度钢(超细贝氏体钢、Q&P钢)在海洋环境中的应力腐蚀开裂行为。结果表明,采用等温工艺的超细贝氏体钢中贝氏体铁素体板条细化,出现了较多的薄膜状残余奥氏体,获得了较高的强度与延伸率。贝氏体铁素体板条与残余奥氏体形成微电偶效应,贝氏体铁素体电位较低作为阳极发生溶解,活性溶解位点诱发裂纹的萌生与扩展。此外,超细贝氏体钢中晶粒较细,塑性变形过程中应力集中较小,薄膜状残余奥氏体对裂纹产生钝化作用,使其具有更低的应力腐蚀敏感性。采用淬火配分工艺的Q&P钢中马氏体板条较为粗短,薄膜状残余奥氏体较少。碳由马氏体分配到残余奥氏体中,马氏体与残余奥氏体形成微电偶效应,电化学腐蚀速率明显增大。Q&P钢组织中的块状残余奥氏体会在应力作用下变形为脆性马氏体,引发应力集中导致裂纹形核,同时产生位错堆积和残余微应力,进一步促进了裂纹的萌生及扩展。The stress corrosion cracking behavior of two advanced high-strength steels(ultrafine bainite steel,Q&P steel)of the same composition in an artificial marine environment 3.5%NaCl solution was studied by means of microscopic characterization(SEM,XRD,EBSD),electrochemical test and slow strain rate stress corrosion test.The results show that being subjected to treatment with isothermal process,the aquired ultrafine bainitic steel presents significantly refined bainitic ferrite laths,companied with more thin film-like residual austenite herewith,presents higher strength and elongation at break.The bainite ferrite lath and residual austenite form a micro-electric couple,the lower potential of bainite ferrite acts as an anode thus suffered from dissolution,while the active dissolution site induces the initiation and propagation of cracks.In addition,ultrafine bainitic steel has fine grain,low stress during plastic deformation,thereby,lower stress corrosion sensitivity,which is due to the passivation of cracks caused by thin film residual austenite.Being subjected to treatment with quenching-partitioning process,the resulted Q&P steel presents thick and short martensitic lath with less amount of thin film residual austenite.However carbon in martensite is partially transferred to the residual austenite,nevertheless,the martensite and residual austenite also form a micro-electric couple,which significantly increases the electrochemical corrosion rate.The blocklike residual austenite in Q&P steel structure may be broken into brittle martensite under the action of stress,causing stress concentration leading to crack nucleation,dislocation accumulation and residual stress,which further promotes crack initiation and propagation.

关 键 词：先进高强度钢 海洋环境 残余奥氏体 电化学腐蚀 应力腐蚀开裂 

分 类 号：TG174[金属学及工艺—金属表面处理]