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某反应堆一回路止回阀密封面发生开裂,影响核电厂安全运行。此阀门的密封面是由铁基耐磨材料NOREM堆焊而成。采用化学成分测定、力学性能试验、金相检验和扫描电镜等分析方法研究了该阀门的开裂原因。该阀门堆焊层的化学成分、力学性能、金相组织都符合要求。该阀门裂纹沿着晶界开裂,裂纹与母材接触部位氧化更严重,此裂纹符合焊接热裂纹的特征。结果表明,发生开裂是该阀门堆焊层材料的本征特性,应调整焊接工艺参数减缓堆焊层的热裂倾向。
A reactor loop check valve sealing surface cracking, affecting the safe operation of nuclear power plants. The valve sealing surface is made of iron-based wear-resistant material NOREM surfacing. The chemical composition, mechanical properties, metallographic examination and scanning electron microscopy were used to analyze the cause of cracking of the valve. The valve surfacing layer of the chemical composition, mechanical properties, microstructure meet the requirements. The valve crack along the grain boundary cracking, the base metal contact with the crack more serious oxidation, the crack in line with the characteristics of welding hot cracks. The results show that the occurrence of cracking is the intrinsic characteristic of the overlay material of the valve. The welding process parameters should be adjusted to slow down the thermal cracking tendency of the overlay.