Accelerated age-hardening kinetics in additively manufactured 18Ni(300) maraging steel

In this comparative study between Laser Powder Bed Fusion (L-PBF) versus conventional hot-rolled 18Ni(300) maraging steel, accelerated age-hardening kinetics was determined due to the variation in annealing behaviour. Conventionally produced 18Ni(300) maraging steel exhibited significant grain growth upon solution annealing at 850-1050 °C, which was not evident in the L-PBF counterpart where oxide particles present in as-built condition inhibited grain growth. Electron Backscatter Diffraction (EBSD) analysis showed higher thermal stability of additively manufactured components up to 1050 °C, where significant grain growth was found in hot-rolled and annealed parts. Despite these differences, both processing routes achieved similar peak hardness after ageing, although L-PBF samples displayed faster initial hardening due to enhanced precipitation kinetics linked to finer grain structure and higher grain boundary density.