Fatigue strength of LPBF Ti6Al4V machined under flood and cryogenic lubri-cooling conditions

In the present work, Ti6Al4V specimens were manufactured by Laser Powder Bed Fusion (LPBF), heat treated and machined using two lubri-cooling conditions, i.e. flood or cryogenic, the latter being useful to improve the machined surface integrity. These specimens were characterised in terms of micro-hardness, microstructure, residual stresses and surface topography. Afterwards, they were fatigue tested under rotating bending loading and the fracture surfaces were analysed by SEM to identify the killer defects. Finally, the experimental fatigue results were compared with the theoretical estimations according to both the Murakami and El Haddad-Smith-Topper models.