Abstract:The superalloy K418 and steel 42CrMo were welded laser. The microstructure of the weld was characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). The mechanical properties of the weld were evaluated by microhardness and tensile strength testing. The results show that the laser weld has non-equilibrium solidified microstructures consisting of FeCrNiC austenite solid solution, and little fine and dispersed Ni3Al ( ) phase, Laves particles and little MC carbides distribute in the interdendritic regions. The average microhardness of the weld is relatively uniform and lower than that of the base metal because the main strengthening phase   partially dissolutes and solidifies quickly after laser. About 88.5% tensile strength of the base metal is achieved in the welded joint because the full penetration welding is gained, and the fracture mechanism is ductility and brittleness. The existence of some Laves particles in the weld also facilitates the initiation and propagation of the microcracks and microvoids and decreases the tensile strength of the welded joint.

Key words: laser welding; weld; microstructure; mechanical properties