Surface integrity factors influencing fatigue crack nucleation of laser powder bed fusion Ti6Al4V alloy

Abstract The quality of the surface influences remarkably the fatigue life of additive manufactured components. This work proposes to study the influence of surface integrity on the bending fatigue life of Ti6Al4V manufactured by laser powder bed fusion. Rectangular specimens were manufactured horizontally and the last printed layer had laser track scanning directions (α=30°,60°,90°) in relation to the specimen length. The top surface 3D-roughness average was similar for all the specimens. The specimens were studied under as-built and heat-treated conditions. A correlation between laser track scanning direction, 2D-roughness parameters, and fatigue life for as-built specimens was found. The as-built specimens with 90° and 30° direction showed the shortest and the longest fatigue life, respectively. Heat-treated specimens showed a shorter fatigue life independently of the surface roughness. This could be explained by other surface integrity factors influencing fatigue performance of the material, such as the presence of subsurface porosity and surface oxygen enrichment.