800MPa级钢悬臂弯曲加载低周腐蚀疲劳表面裂纹扩展特性研究

在悬臂弯曲加载方式下,研究了800MPa级10CrNiMo结构钢在3.5%NaCl水溶液中的低周腐蚀疲劳表面裂纹扩展特性,采用金相显微镜、扫描电子显微镜及X射线能谱仪观察并分析了腐蚀疲劳试样断口,与空气中相同加载方式下该材料的低周疲劳表面裂纹扩展速率进行了比较,结果表明,在表面裂纹扩展初期,在3.5%NaCl水溶液中的表面裂纹扩展速率较空气中的快,但随着总应变范围的增加,这种快的趋势在逐渐减小,当总应变范围达到约1%时,在两种环境中的表面裂纹扩展速率基本相当;在表面裂纹扩展的后期,裂纹内部聚集了大量的腐蚀产物,该腐蚀产物主要为铁的氧化物,氧化物的存在增加了裂纹扩展的闭合效应,减缓了表面裂纹的扩展。

Study on Surface Crack Propagation Characteristics of 800MPa Steel in Corrosion Circumstance under Cantilever Bend Loading

Under cantilever bend loading,surface crack propagation characteristics of 800MPa grade 10CrNiMo structural steel in 3.5% NaCl aqueous solution were studied and the surface crack propagation rate(SCPR)of the steel in such corrosion circumstance was compared with that in air.The results manifest that at the beginning of surface crack growth,SCPR is quicker in 3.5% NaCl aqueous solution than that in air,while as the total strain range increasing,this difference of SCPR becomes less and less,and when the total strain range is near to 1%,the SCPRs are basically equivalent in two different environments.Corrosion fatigue specimen fracture appearance was observed under metallurgical microscope,scanning electric mirror and X-ray energy spectrum equipment and the results indicate at the late stage of surface crack propagation,many corrosion products such as ferrous oxides were found to be accumulated inside the crack,which increase close-effect of surface crack propagation and retard its growth.