Analysis of Ni interlayer effects on laser beam welding of dissimilar pure Mo alloy to stainless steel

Abstract

The effect of Ni interlayer thickness on chemical composition, microstructure and mechanical properties of laser welding of Mo and stainless steel was analyzed systematically. Experimental results indicated that with the increase in thickness of Ni interlayer, the number of MoFe IMCs, the hardness at the Mo-FZ interface, the width and grain size in the heat affected zone of Mo side and the thickness of MoFe IMCs layer decreased significantly. The maximum tensile strength attained 351 MPa for joints with 0.1 mm thick Ni interlayer. With excessive (>0.1 mm) Ni addition in the welded joint, the mechanical properties deteriorated due to the formation incomplete fusion, void and crack defects. The tensile investigation showed that the weakest area of the joint was MoFe IMCs layer. When an appropriate thickness of Ni interlayer is used, the MoFe IMCs layer can be strengthened by increasing diffusion ability of Mo to FZ and Ni concentration in the MoFe IMCs and restraining of MoFe IMCs, consequently producing high-quality welded joints.