【摘要】 应用控制电位慢应变速率拉伸试验方法,研究了新型无镍超高强度结构钢40CrMnSiMoVA(σ_B=1800～2000MPa)在典型模型环境3.0%NaCl 和蒸馏水中的电化学特性和应力腐蚀敏感性。研究结果表明,该钢对应力腐蚀开裂十分敏感,与空气中相比,3.0%NaCl 中开路电位下的断裂总应变εf 降低约四分之一。而在阳极极化(-640mV)和阴极极化(-1250mV)电位下,εf 的降低进一步增大,相应为空气中的42%和56%。溶液不除氧时,这种延性降低明显减少,-640mV 时εf 的降低值仅及相同电位除氧条件下的一半。扫描电镜分析表明,在腐蚀断裂区断口均呈典型沿晶破坏,并有二次裂纹分布其上。可以认为,40CrMnSiMoVA 钢在水溶液中的应力腐蚀开裂机理不是纯氢脆,而是局部阳极溶解与氢脆共同作用的氢助应力腐蚀开裂(HAC)。更多还原

【Abstract】 The susceptibility to Stress Corrosion Cracking (SCC) of a new type of aircraft structural ultra-high strength steel 40CrMnSiMoVA in simulated envi- ronments (3.0% NaCl solution and distilled water)is evaluated and a modified SCC failure mechanism of high strength steel is suggested through experimental investigation using slow strain rate tension technique at different applied po- tentials;Both micro- and macro- fractographic analyses were conducted using SEM and microscope.It has been found that 40CrMnSiMoVA steel is relatively sensitive to SCC in aqueous solution,and the SCC behavior is significantly influenced by the applied potentials,the strain rate,and even the existence of oxygen in solution.The experimental results showed that the total elongation to fracture ε_f of the steel in aqueous solutions at open circuit potential decreased to 75% of that in air.Both anodic and cathodic polarization reduced the ductility further,ε_f at -640mV and-1250mV decreased to 58% and 44% of that in air respectively.The deaeration of solution,however,made the total elongation reduction more than that in aerated solution,ε_f reduction in 3.0% NaCl at -640mV under deaeration was almost two times of that at the same potential without deaeration.SEM fractographic examination showed that the intergra- nular fracture was typical for all specimens tested in aqueous solutions,and the secondary cracks could be seen on all specimens in the intergranular fai- lure region.According to the experimental results,it is suggested that the SCC mechanism of high strength steel involved should be rather the combined ac- tion of local anodic dissolution at the crack tip and hydrogen assisted cracking (HAC) than pure hydrogen embrittlement.更多还原