14Cr17Ni2钢制螺栓的断裂原因分析

Analysis on fracture cause of 14Cr17Ni2 steel bolt

利用光学显微镜、扫描电镜分别观察了14Cr17Ni2钢制断裂螺栓的显微组织和断口形貌。同时,采用常规拉伸和慢应变速率拉伸试验分别对断裂螺栓的常规力学性能和氢脆敏感性进行了检测和评价。结合有限元分析,对14Cr17Ni2钢制螺栓发生断裂的原因和机理进行了探讨和分析。结果表明,14Cr17Ni2钢制螺栓的断口特征属于沿晶＋穿晶准解理脆性断口,慢应变速率拉伸试验结果显示14Cr17Ni2钢制断裂螺栓存在氢致延迟断裂风险,14Cr17Ni2钢制螺栓在使用工况下发生阴极析氢型应力腐蚀现象,钢中氢含量较高。断裂螺栓基体中氢含量及有限元模拟结果侧面阐释了14Cr17Ni2钢制螺栓发生氢致延迟断裂的根本原因。

Microstructure and morphologies of broken bolt made of 14Cr17Ni2 steel were observed by means of OM and SEM.Meanwhile,with the conventional tensile test and slow strain rate tensile test,the mechanical properties of 14Cr17Ni2 steel were obtained and hydrogen embrittlement susceptibility evaluated.Combined with the finite element simulate analysis,the root cause and mechanism of broken bolts were analyzed.The results show that the fracture are featured with a mixed morphologies of dimples,quasi-cleavage and intergranular features for the 14Cr17Ni2 steel bolts.The type of failure is hydrogen induced delayed fracture.The results of failure analysis are proved by the hydrogen concentration determination and the finite element simulation.