蒸汽发生器手孔镍基合金堆焊层开裂分析

Analysis on cracking mechanism of nickel based alloy buttering of steam generator hand hole

蒸汽发生器是核电厂主要的承压边界,某核电厂蒸汽发生器手孔152镍基合金堆焊层发生开裂,对核电安全、经济地运行造成一定影响。预制手孔模拟件复现缺陷并分析开裂处的微观特征,采用横向可调拘束试验分析152熔敷金属的开裂倾向,并利用有限元分析手孔堆焊层的塑性应变分布,复现出了与实际缺陷特征和位置一致的裂纹,发现152堆焊层开裂位置处存在长条状、颗粒状碳化物沿晶界析出,明确了蒸汽发生器手孔152堆焊层开裂机理为碳化物诱导型高温失塑裂纹(DDC),碳化物在晶界析出与焊接应变共同作用导致手孔堆焊层发生开裂。

Steam generator is the main pressure boundary of nuclear power plant.Cracking was discovered on the 152 nickel base alloy buttering of steam generator hand hole in a nuclear power plant,which caused a certain impact on the safe,reliable and economic operation of the nuclear power plant.In this paper,defects were reproduced on the hand hole mockup,and the micro characteristics of cracks were analyzed.The cracking tendency of 152 deposited metal was analyzed by transverse adjustable restraint test,and the plastic strain distribution of hand hole buttering was analyzed by finite element method.The characteristics and the positions of the reproduced cracks were consistent with the actual defect.It is found that there are long strip and granular carbide at the cracking position.The results show that the cracking mechanism of the hand hole 152 buttering was carbide induced ductility dip cracking(DDC),the combined action of carbide precipitation and welding strain led to cracking of the hand hole buttering.