The mechanical properties and interface bonding mechanism of Molybdenum/SUS304L by laser beam welding with nickel interlayer

Abstract

The capability of joining molybdenum (Mo) to 304L stainless steel (304L) is of significance for nuclear energy industry, while no effective methods have been developed to produce high strength joints. Laser beam offset welding was used to join pure Mo and 304L. The results demonstrate that: (i) when laser beam shifts to 304L for 0.1 mm, the performance of joints are the best and tensile strength is about 110 MPa; (ii) by presetting a nickel (Ni) foil at Mo/304L interface, tensile strength of the joints is increased to about 280 MPa; (iii) after adding Ni, diffusion ability of Mo at Mo/FZ interface increases and diffusion depth of Mo rises from 7.4 μm to 9.7 μm; content of Mo in fusion zone (FZ) rises, so that the microhardness of FZ increases from 175 HV to 220 HV, which is close to that of the HAZs of Mo and 304L, and the gradient of microhardness of the joints obviously decreases; moreover, Mo-rich grains inserting into FZ are found at Mo/FZ interface after adding Ni and the depth of insertion in can be up to 20 μm. These results are favorable for improving bonding strength of Mo/FZ interface, as well tensile strength of Mo/304L joint. Keywords: Laser welding, Dissimilar joint, Pure molybdenum, 304L, Minor Ni addition