Enhancement of surface quality in powder bed fusion using a laser beam by flat-top laser beam profile control

A powder bed fusion using a laser beam process incorporating a flat-top beam was developed to improve the fabrication quality of Ti–6Al–4V (Ti64). To evaluate the influence of the fabricated structures, the denudation zone (DZ) was measured as a key indicator through single-bead and single-layer fabrication experiments. The main objective was to clarify the correlation between DZ formation and ambient pressure under flat-top beam irradiation, with reduced-pressure conditions introduced primarily to understand the underlying physical mechanisms. In this study, Ti64 powder was irradiated by a flat-top beam at output powers of 150–250 W and scanning speeds of 80–180 mm/s. It was found that decreasing the ambient pressure from 105 to 103 Pa reduced the DZ width, whereas further reduction to 102 Pa caused the DZ to expand. The minimum DZ width of 100.5 μm was obtained at 103 Pa.