某核电厂循泵联轴器螺母开裂失效原因分析

Analysis on Cracking Failure of Coupling Nut of Circulating Pump in a Nuclear Power Plant

核电厂日常运行期间一循环水泵吸水室墙壁内出现有异音,对其进行解体检修中发现循环水泵中间轴联轴器的两颗个螺母断裂失效。通过对失效部件进行宏观观察、化学成分分析、硬度测试、微观组织测试和微观形形貌观察等测试手段,发现螺母因热处理工艺控制不当,导致螺母材料组织存在缺陷,降低了材料的塑性和冲击韧度,螺母在应力腐蚀开裂敏感环境中服役,受S离子和应力作用发生应力腐蚀开裂失效。

During the daily operation of the nuclear power plant,there was abnormal sound in the wall of the suction chamber of a circulating water pump.During its disassembly and maintenance,it was found that the two nuts of the coupling between the intermediate shafts of the circulating water pump were broken and failed.By means of macro observation,chemical composition analysis,hardness test and micro observation of the failed parts,it was found that the improper control of the heat treatment process of the nut lead to the defects in the structure of the nut material and reduced the plasticity and impact toughness of the material.When the nut was used in the stress corrosion cracking sensitive environment,the stress corrosion cracking failure occured under the action of s ion and stress.