Mixed fluxes for Nimonic263 superalloy A-TIG welding and its effect

Ternary orthogonal experiment was employed to examine the efficiency of the intermixture of single-ingredient welding fluxes to increase the penetration depth on Nimonic263 superalloy. The experiment results show that the efficiency of NaF-MgF₂-CaO and NaF-MgF₂-CaF₂ mixed flux is obvious. Compared with conventional TIG welding, the welding penetration increased 122% by the action of the mixed flux which is composed of NaF, MgF₂ and CaF₂ and their proportion is 5:6:5; nevertheless the penetration increased 164% by the action of the mixture composed of NaF:MgF₂:CaF₂ = 5:4:1. Tensile test result indicates that the fracture strength of weld bead of the second flux is higher than base metal under almost all the welding parameters, and it increases along with the decrease of the welding current and velocity. The plasticity of the weldment is perfect, and the average specific elongation is over 100%. The results of fracture analysis elucidate that the dimples on the fracture section of the weld bead is deeper and distributed more homogeneous than that on the section of the base metal.