Weldability of super-Ni/NiCr laminated composite and 18-8 stainless steel

Super-Ni laminated composite and 18-8 stainless steel were welded together by tungsten inert gas arc welding with filler metal. Microstructure, microhardness and phase constitution near the fusion was analyzed by means of micro-image analyzer, electron probe micro-analyzer and X-ray diffraction. Experimental results indicated that the columnar austenite grains at the weld edge grew with directionality, which were perpendicular to the fusion zone. A reliable fusion zone was formed between the NiCr base layer and the welded metal. Microhardness near the super-Ni cover layer increased, while the microhardness of welded metal near the 18-8 steel was lower than that of the 18-8 base metal. The welded metal mainly consisted of austenite, a little δ ferrite, γ-Ni (Cr, Fe) and FeNi. The tungsten arc in the welding should be controlled towards the 18-8 steel side to avoid the excessive molten lose of super-Ni cover layer.