Rotating Bending Fatigue Behavior of Additively Manufactured Ti6Al4V Specimens Subjected to CO2 Laser Polishing

Abstract In this work, the rotating bending fatigue (RBF) life of Ti6Al4V alloy specimens produced through laser-powder bed fusion (L-PBF) and electron beam-powder bed fusion (E-PBF) was assessed. The RBF tests were carried out on specimens in the as-built condition and after CO 2 laser polishing, according to the process parameters found elsewhere. The RBF tests were carried out at 300, 600 and 900 MPa of nominal applied stress and considering specimens built vertically onto the build platforms. The results, analyzed in terms of 3D texture surfaces, fracture surfaces and microstructure, showed a different response of specimens against the fatigue testing. The E-PBF specimens retained a high surface roughness compared to the L-PBF ones after polishing. A notable RBF life increase was obtained for both the L-PBF and E-PBF specimens, showing also a good correlation with the stress levels. The RBF life of the L-PBF and E-PBF specimens after polishing increased by 26 and 1% respectively for the high-stress condition, the 127 and 113% respectively for the medium-stress condition and by 103 and 59% respectively for the low-stress condition. The results also showed that the RBF life of E-PBF specimens was more sensitive to the presence of subsurface defects as well as to specific microstructure features, whereas for the laser-polished L-PBF specimens, the rupture occurred at the boundary between the as-built and polished areas.