Process optimisation on fatigue performance of additive manufactured Ti-6Al-4V in high layer thickness for PBF-LB/M

Laser-based powder bed fusion of metals (PBF-LB/M) is an additive manufacturing technology capable of producing complex geometries with minimal post-processing. However, fatigue performance of PBF-LB/M components is often inferior to conventionally manufactured counterparts due to process-induced defects. This study investigates the influence of layer thickness and process parameters on the density, mechanical properties, and fatigue behaviours of Ti-6Al-4V specimens fabricated via PBF-LB/M. Specimens built with 30-µm, 60-µm, and 90-µm layer thicknesses consistently achieved relative densities ≥99.9%, and specimens built with 130-µm layer thicknesses achieved relative density ≥99.8%. Tensile testing demonstrated that all specimens except for the elongation of specimens built in 130-µm layer thickness met ASTM F2924-14 requirements. Fatigue testing revealed that specimens built with 90-µm layers exhibited comparable performance to those built with finer layers. Fractography shows fatigue crack initiation dominated by surface defects rather than internal porosity. Process optimisation enabled theoretical volume production rate increases of up to 334.82% and 389.90% for 90 and 130-µm parameters respectively. These findings demonstrate that PBF processed Ti-6Al-4V parts in high layer thickness can maintain structural reliability while enhancing build efficiency, providing a viable pathway toward industrial-scale mass production of Ti-6Al-4V components.