Surface modification and mechanical properties of laser powder bed fusion Inconel 718 after magnetic-assisted laser polishing

Industrial application of additive manufactured (AM) metal components are hindered by high rough surface. The current study focuses on instability control of laser polished molten pool on basis of magnetic-assisted technique to obtain smooth surface. Both surface topography and microstructure development of the magnetic-assisted laser polished layer has been quantitatively characterized via laser confocal scanning microscopy (LCSM), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and X-ray diffractometer (XRD). Results indicate that compared to conventional laser polishing, Ra value of roughness can be further decreased by more than 98% while chemical element micro-segregation lead to more strengthen γ″ phase formation. Correspondingly, the current surface exhibits higher sub-surface microhardness, lower residual tensile stress, and better tensile property. This study demonstrates the feasibility of magnetic-assisted laser polishing on surface modification, and clarifies the mechanism of surface enhancement together with complementary multiphysics simulations of laser-magnetic-metal interactions.