High-vacuum laser treatments enhance strength, ductility and fatigue limit of additively manufactured stainless steel

Post-process laser scanning under high vacuum is proposed as a non-isothermal heat treatment to simultaneously refine the intragranular microstructure near the surface and reduce surface roughness, while also preventing oxidation, in order to enhance the overall mechanical response of an alloy. This treatment is performed using laser spot sizes and scan speeds that produce higher temperature gradients and faster heating/cooling rates than those encountered during manufacturing. The effectiveness of this approach is demonstrated on laser-based direct energy deposited (LDED) 316L stainless steel using parameters similar to those used in laser-based powder bed fusion (LPBF). High vacuum (