Microstructure and mechanical properties of deposited metal for nuclear plant nickel alloy welding wire

Microstructure and mechanical properties of deposited metal with experimental nickel alloy wires by GTAW was investigated by JMatPro software, OM, SEM, TEM etc. Results indicated that there were columnar γ matrix, interdentritic precipitates including σ phase, MC carbides, Laves phases in the deposited metal. Compared with nominal chemical compositions, dendrite core has higher Fe content and lower Nb, Mo content, while interdendritic segregation zone has higher Nb, Mo content and lower Fe content. MC carbide was (Nb,Ti)C, Laves is rich in Mo and Cr with structural formula (Ni,Cr,Fe)₂(Nb,Mo), σ phases is rich in Mo and Cr with MoCrFe tetragonal structure. The deposited metal has high strength and good ductility at room temperature and 350 ℃. Dimples along grain boundary dominants the fracture morphology of tensile specimen at room temperature, with dense precipitates in the bottom of dimples.