On the role of building orientation and surface post-processes on the fatigue life of Ti-6Al-4V coupons manufactured by laser powder bed fusion

Additive manufacturing (AM) techniques have been rapidly expanding due to their ability to produce complex geometries with an efficient material use. However one of the main drawback of AM technologies is the poor surface quality especially for what concerns powder based techniques. In order to design reliable AM parts, the material mechanical properties resulting from the manufacturing process need to be properly characterized. The present study investigates the fatigue of miniaturized Ti-6Al-4V specimens manufactured using laser powder bed fusion (L-PBF) along three different building orientations. In order to improve the surface quality, two post-treatments were applied to the test coupons, i.e. electro-plasma polishing and machining. Fatigue test results highlight how the post-treatments improve the fatigue properties of L-PBF Ti-6Al-4V samples with machined samples outperforming all the others conditions. Data gathered from the experimental campaign have been used to generate a predictive tool to account for surface quality, that can be used to foresee fatigue properties of Ti-6Al-4V samples subjected to different surface treatments.