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Abstract: Exploratory experiments of laser welding cast Ni-based superalloy K418 turbo disk and alloy steel 42CrMo shaft were conducted. Microstructure of the welded seam was characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive spectrometer (EDS). Mechanical properties of the welded seam were evaluated by microhardness and tensile strength testing. The corresponding mechanisms were discussed in detail. Results showed that the laser-welded seam had non-equilibrium solidified microstructures consisting of FeCr0.29Ni0.16C0.06 austenite solid solution dendrites as the dominant and some fine and dispersed Ni3Al γ′ phase and Laves particles as well as little amount of MC short stick or particle-like carbides distributed in the interdendritic regions. The average microhardness of the welded seam was relatively uniform and lower than that of the base metal due to partial dissolution and suppression of the strengthening phase γ′ to some extent. About 88.5% tensile strength of the base metal was achieved in the welded joint because of a non-full penetration welding and the fracture mechanism was a mixture of ductility and brittleness. The existence of some Laves particles in the welded seam also facilitated the initiation and propagation of the microcracks and microvoids and hence, the detrimental effects of the tensile strength of the welded joint. The present results stimulate further investigation on this field. [Copyright &y& Elsevier]

High Nb containing TiAl alloys have prospect to be used for turbo wheel and exhaust valve for vehicle engine. Friction welding is a suitable process for fabricating these components. For investigating the weldability of these alloys, cylindrical samples of Ti–45Al-8.5Nb-0.2W-0.2B-0.02Y (in at%) alloy with a diameter of 10 mm were welded by continuous drive friction welding process, and the microstructures and the mechanical properties of the joints were analyzed in this paper. The results showed that the weldability of the present alloy was very good. At parameters of rotational speed of 2400 r/min, friction pressure of 320 MPa, burn-off distance of 3 mm and upset pressure of 360 MPa, completely metallurgical bonding interfaces were obtained. The joint had a severely plastic deformation zone (SPDZ) with a biconcave lens geometry. The thicknesses of the center and periphery of SPDZ were about 40 μm and 800 μm, respectively. There existed a transition zone (TZ) between parent metal (PM) and SPDZ. SPDZ exhibited the deformation flow lines and had a randomly-oriented recrystallized duplex (DP) microstructure with the average grain size of 2.5 μm, in contrast, PM presented a nearly lamellar (NL) microstructure with a colony size of 150 μm. TZ showed a mixture microstructure combining deformed lamellar colonies and partially recrystallized grains. At room temperature, 750 °C and 800 °C, welding joints had better tensile properties than PM. • As-cast Ti–45Al-8.5Nb-0. 2W-0. 2B-0. 02Y alloy has good friction weldability. • The joint had a severely plastic deformation zone with a biconcave lens geometry. • Fine-grained DP microstructure of welding joint showed random orientation. • Welding joint had better tensile properties than parent metal. [ABSTRACT FROM AUTHOR]