某核电机组LLS柴油发电机排气管与汽缸连接螺栓发生断裂。通过宏观及微观分析、化学成分分析、显微组织分析、力学性能测试等方法，对螺栓的断裂原因进行了分析。结果表明：该GH2036合金螺栓的失效模式为沿晶脆性断裂；失效原因为螺栓热处理工艺不当，导致晶界析出了薄片状脆性相，弱化了晶界，造成螺栓在高温和应力共同作用下产生了沿晶脆性断裂。

Joint bolts which connected the exhaust pipe and the cylinder on the LLS diesel engine generator set fractured in a nuclear power plant unit. By means of macroscopic and microscopic analysis, chemical composition analysis, microstructure analysis, mechanical property test and so on, the fracture reasons of bolts were analyzed. The results show that:the failure mode of the GH2036 alloy bolts was intergranular brittle fracture; the failure reasons were that the heat treatment process of the bolts was improper, resulting in the precipitation of lamellar brittle phase along the grain boundary; the phase weakened the grain boundary, which induced that the intergranular brittle fracture occurred to the bolts under the action of high temperature and stress.