电厂旁路阀盖Inconel 718螺栓失效分析

Fracture Failure Analysis of Inconel 718 Bolt of Bypass Valve Cover Stud in Power Plant

针对某电厂旁路阀盖Inconel 718螺栓断裂事件进行失效分析。通过化学成分分析、宏观形貌和显微组织观察、力学性能测试和断口微观形貌观察等方法对螺栓的断裂原因进行研究。结果表明:裂纹是从螺栓一侧起始,在应力作用下扩展最终断裂。金相分析和扫描电镜分析的结果可知,断面附近螺纹根部较粗糙,组织存在混晶,开裂主要为脆性沿晶开裂。故螺栓断裂失效主要是由于存在混晶组织导致螺栓的脆性沿晶开裂。

Failure analysis was carried out for the fracture event of Inconel 718 bolt on the bypass valve cover of a power plant. The fracture reason of the stud was studied by means of chemical composition analysis, macro morphology and microstructure observation, mechanical property test and fracture morphology observation. The results show that the crack starts from one side of the stud, expanding under stress until fracture. The results of metallographic analysis and scanning electron microscope analysis show that the root of the thread near the section is rough, the structure has mixed crystals, and the cracking is mainly brittle intergranular cracking. Therefore, the fracture failure of studs is mainly due to the brittle intergranular cracking of studs due to the existence of mixed crystal structure.