The effects of recrystallisation on the fatigue and corrosion properties of LB-PBF stainless steel 316L

• In LB-PBF SS316L, recrystallisation begins at ≥ 1150 °C, fully achieved at 1200 °C. • High temperature treatments reduce but do not remove mechanical anisotropy. • Full recrystallisation improves pitting resistance in 3.5 % NaCl. • Heat treatment balances strength, ductility, fatigue and corrosion properties. This study investigates the influence of post-build heat treatments (HTs) on the microstructural evolution, mechanical performance, and corrosion resistance of laser beam powder bed fusion (LB-PBF) stainless steel 316 L. Samples built in vertical and horizontal orientations were subjected to three HT conditions (1050, 1150, and 1200 °C), enabling analysis of recrystallisation behaviour, grain morphology, and the mitigation of anisotropy. Tensile, low-cycle fatigue (LCF), and fatigue crack growth (FCG) testing revealed that full recrystallisation occurred at ≥ 1150 °C, reducing orientation-dependent discrepancies in strength and ductility. Despite improved isotropy, LCF testing demonstrated residual anisotropy, with samples built in the vertical orientation consistently outperforming those built in the horizontal orientation. Samples heat treated at 1050 °C retained a fine, columnar grain structure, resulting in superior resistance to crack growth due to increased yield strength and grain boundary density. In contrast, samples heat treated at 1150 and 1200 °C exhibited coarser, equiaxed grains with diminished fatigue crack resistance. Cyclic polarisation testing showed recrystallisation at the higher temperatures induced positive changes in corrosion performance, substantially increasing pitting potential compared to un-recrystallised microstructures, as found at 1050 °C. The findings highlight the trade-offs between strength, ductility, and fatigue resistance as a function of microstructure, offering insight into optimising HT protocols for LB-PBF SS316L components in fatigue-critical applications.