Yi Zheng1
Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University1
Yi Zheng1
Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University1
Improving formability and mechanical properties has always been one of the challenges in the field of additive manufacturing (AM) of nickel-based superalloys. In this work, the effect of a coaxially coupled alternating magnetic field (AMF) on surface morphology and mechanical properties of plasma arc additive manufactured Inconel 718 deposit were investigated. The exploratory experiments involve two aspects: (i) the effect of different AMF parameter on the morphology and grain structure of the single-pass bead was explored and (ii) an appropriate AMF (30Hz, 12mt) parameter was selected for the fabrication of a 20-layer Inconel 718 thin-walled deposit. Results show that the electromagnetic stirring promoted grain refinement of the single-pass bead, and the finest grains were achieved with AMF of 12mt and 30Hz. The Lorentz force induced by AMF strongly changes the flow behavior of the plasma jet and the molten pool, suppressing the tendency of the liquid metal in the molten pool to flow down on the two side face of deposit, which in turn remarkable improved the surface accuracy of the thin-walled deposit. Furthermore, the electromagnetic stirring induced by AMF can effectively enhance the convection between the dendrites, which could not only contribute to the formation of finer dendrites but also alleviates the enrichment of the elements (i.e., Nb and Mo) at solid-liquid interface and inhibits the precipitation of Laves phase. The smallest primary dendritic arm spacing (~13 μm) and lowest Laves phases area fraction (3.12%) were witnessed in the bottom region of the AMF-assisted deposit. The mechanical test confirmed that the microhardness of the deposit was moderately improved and the tensile properties were slightly enhanced compared with the counterpart without AMF. This paper provides guidelines for tailoring the microstructure and the mechanical properties of Inconel 718 via AMF, indicating the significant application potential of AMF for the arc-based AM process.