A comprehensive investigation on microstructure and mechanical properties optimisation of 316L stainless steel produced by laser-based powder bed fusion

Purpose This study aims to introduce an algorithm that can successfully define optimum laser-based powder bed fusion (LB-PBF) processing and post-heat treatment parameters for manufacturing 316L stainless steels with limited energy usage and enhanced properties. Design/methodology/approach Taguchi’s design of the experiment (DoE) was elaborated to define the ideal LB-PBF process and heat treatment parameters. Based on the DoE and experimental results, the LB-PBF energy density between 6.7 J/mm3 and 14.7 J/mm3 produced parts with a volumetric mass density of 98.8% or higher. The authors’ proposed processing window shows 316 L manufactured products can reach the highest mechanical strength reported in literature. Findings The microstructure characteristics of the enhanced 316L builds showed characteristic dislocation density, grain size and texture features. The proposed heat treatments at 650, 870 and 1,150 °C results in preferential grain growth up to approximately 45 µm, reorienting the as-built grain structure from < 100> to < 101> components. This promoted mechanical twinning propensity and the dynamic Hall–Petch effect, resulting in significant improvements in the mechanical properties. Originality/value The manufactured parts in the optimised conditions achieved improvement in ultimate tensile strength (970 MPa) and elongation (32%), representing a noticeable strength–ductility combination for LB-PBF of 316L.