核级ENiCrFe-7镍基合金焊条熔敷金属组织与性能研究

Study on microstructure and properties of nuclear-grade Ni-base ENiCrFe-7 welding electrodes filler metals

通过焊芯化学成分和药皮配方优化设计,研制出核级ENiCrFe-7镍基合金焊条。应用金相显微镜观察熔敷金属的显微组织,电子扫描显微镜对断口进行形貌观察并分析断裂机理,EDS分析晶界和晶内的析出产物;测试熔敷金属的力学性能和耐晶间腐蚀性能。结果显示:ENiCrFe-7镍基合金焊条熔敷金属的显微组织为奥氏体柱状晶,一些细小析出物分散沉淀于晶粒内及晶界上。强度、延伸率、弯曲、晶间腐蚀均满足验收标准,冲击功良好,超过验收标准80%。拉伸断口呈现出典型的韧性断裂形貌。EDS分析发现熔敷金属的晶粒内及晶界处存在含Cr、Fe的金属化合物和Ti、Al的氧化物以及含Nb元素的金属化合物第二相质点。

The nuclear-grade Ni-base ENiCrFe-7 welding electrodes were developed by the optical designing of coating formula and composition of core wire.The microstructure of ENiCrFe-7 filler metals was observed by optical microscopy.The fracture morphology was observed and fracture mechanism was analyzed by scanning electron microscopy(SEM).The precipitates of grain and grain bound-aries were determined by energy dispersive spectrometer(EDS)on the SEM.The mechanical properties and intergranular corrosion resistance were tested.The results showed that the microstructure of ENiCrFe-7 filler metals was columnar austenite;the very small precipitates were observed at the grain and grain boundary.The strength,elongation,bending property and intergranular corrosion resistance of filler metals were qualified,and the impact properties performs well,which was more than 80%of the technical requi-rements.The fracture morphology was ductile fracture.The metal compounds contained Cr,Fe,metallic oxides contained Ti,Al and second-phase particle contained Nb were found along the migrated grain boundaries by EDS.