反应堆压力容器用Ni-Cr-Mo-V钢焊缝热老化脆化行为研究

Thermal Ageing Embrittlement Behavior of Ni-Cr-Mo-V Steel Weld Metal for Reactor Pressure Vessel

对反应堆压力容器用Ni-Cr-Mo-V钢焊缝温度监督样品的热老化脆化行为进行了研究。焊缝属于压力容器的薄弱环节,服役时间最高达120 430h(服役温度归一化到300℃)。3批次的焊缝监督样品冲击实验表明,焊缝材料在热老化过程中发生了脆化。通过研究发现,金相组织和显微维氏硬度在热老化期间未发生明显的变化,表明在热老化过程中不存在硬化脆化机制。断口分析及扫描俄歇纳米探针研究表明,晶界发生了P的偏析,弱化了晶界结合力,因此,反应堆压力容器用Ni-Cr-Mo-V钢焊缝在热老化过程中发生了由杂质元素P偏析引起的非硬化脆化。

The study of thermal ageing embrittlement of temperature sets of reactor pressure vessel surveillance Ni-Cr-Mo-V steel weld metal was conducted.Weld metal is the weakness of the reactor pressure vessel and its service time gets to 120 430 h（the operating temperature is normalized to 300℃）.The impact test of the 3 batches of weld surveillance sample indicates that the weld metal is embrittled during thermal ageing.Through the study,significant change is not found in the microstructure and microVickers hardness during thermal ageing,indicating that there is no hardening embrittlement mechanism in the thermal ageing process.The study of impact fracture and Auger electron spectroscopy indicates that the impurity element P segregates to thegrain boundaries and lowers their cohesion during the long-term thermal ageing.Therefore,the reactor pressure vessel Ni-Cr-Mo-V steel weld metal occurs non-hardening embrittlement which is probably caused by the intergranular segregation of impurity element P during the long-term thermal ageing.