Effect of Heat Treatments on Fatigue Properties of Ti–6Al–4V and 316L Produced by Laser Powder Bed Fusion in As-Built Surface Condition

Abstract

Over the last decade, additive manufacturing (AM) techniques have been expanding rapidly due to their ability to produce complex geometries with an efficient use of material. In order to design reliable AM parts, the mechanical properties resulting from the manufacturing process need to be understood. The present study investigates the fatigue of AM Ti–6Al–4V and 316L. Miniaturized Ti–6Al–4V and 316L specimens were manufactured using laser powder bed fusion (L-PBF). The geometry, process parameters, and loading conditions were kept constant and the specimens were tested in as-built surface condition. The S-N curves of as-built, stress-relieved and HIP’ed specimens were measured, and an analysis of the microstructure, relative density and surface roughness was performed. The effect of fatigue influencing factors (residual stresses, surface roughness, porosity and microstructure) was systematically investigated. In order to understand the fatigue failure mechanism, identification of crack initiation point, via fracture surfaces analysis, was performed.