On the effect of small laser spot size on the mechanical behaviour of 316L stainless steel fabricated by L-PBF additive manufacturing

This research effort experimentally investigated the influence of small laser spot size (LSS – 50 µm and 100 µm) on the mechanical behaviour of additively manufactured 316 L Stainless Steel (SS) samples produced by laser-powder bed fusion on a single metal 3D printer. The effect of main process parameters including scanning speed (1400, 1700 and 2000 mm/min), layer thickness (30, 55, and 80 µm), build direction (0°, 15° and 30°, 90 ° or flat) and printing power (100, 200, and 350 W) was analysed. Tensile tests together with scanning electron microscopy were carried out to determine the mechanical behaviour and fractography pattern of the parts produced with different parameters. When changing the build direction, the results led to a nearly isotropic mechanical behaviour in combination with the manufacturing equipment. By employing small laser sport size, the melt pool depth was increased, which in turn led to an enhancement in the mechanical performance of the fabricated 316L SS. Printed specimens displayed ultimate tensile strength values of 165–550 MPa (LSS of 50 µm) and 147–519 MPa (LSS of 100 µm), yield strengths of 137–402 MPa (LSS of 50 µm) and 120–385 MPa (LSS of 100 µm), with an elongation at break of 5–64%.