Surface remelting effect on overhanging region surface roughness of thin-walled Inconel 718 fabricated by laser powder bed fusion

The industrial deployment of laser powder bed fusion (LPBF) for intricate arc-surface thin-walled components is often limited by poor surface quality in overhang regions. This study employs Inconel 718 to elucidate the influence of contour parameters on overhang surface roughness. A Taguchi experimental design, combined with signal-to-noise (S/N) main-effect analysis, was employed to optimise processing parameters. Scanning electron microscopy (SEM) was utilised to characterise surface micro-morphology. The results indicate that setting laser power and scanning speed to 180 W and 650 mm/s, respectively, markedly suppresses dross formation. Subsequent laser in-situ remelting further mitigates adhering powder, spherulization, and lack of fusion defects. Simulation of the contour remelting process shows that applying counter-pressure appropriately expands the contour melt pool width, enhancing the wetting interaction between the contour and the core melt tracks. Implementing this parameter control strategy without altering the hatch parameters significantly reduces the post-processing requirements for arc-surface thin-walled overhangs. It also clarifies the defect-formation mechanism that is dominated by contour parameters and establishes a technical foundation for the rapid fabrication of high-performance hollow-closure structures.