Effect of Surface Finish on Fatigue Properties of Ti Gr23 Alloy Produced by L-PBF and to Be Used for Human Implants

Ti Gr23 alloys are widely used in the manufacture of human implants and have recently been produced by L-PBF (Laser Powder Bed Fusion) techniques due to their good mechanical properties combined with good biocompatibility. The fatigue properties of these components are very important and are influenced by many parameters such as: surface finish, residual stresses and internal defects. This paper presents a detailed study of the effect of surface finish on the fatigue properties of Ti-Gr23 alloy produced by L-PBF. In this case, the samples are all produced in the vertical direction using two different LASER conditions. One part of the specimens was analysed under as-built conditions, one part was sandblasted and the last part was manually polished. The surface texture was then analysed using a stylus profilometer. Mechanical properties were then assessed by tensile tests and microhardness profiles acquired on specimens used for mechanical testing. Fatigue tests were then carried out under load control at R = −1 with a frequency of 40 Hz, starting from an initial stress of 40% of the tensile strength of the material. The fatigue limit was calculated using the Dixon Mood approach. A detailed SEM analysis of the fracture surface was carried out to determine the causes of failure in the failed specimens. The results obtained were then used to evaluate the local fatigue limit near the crack nucleation site using the Murakami model. The results showed an improvement in the fatigue properties of the surface treated specimens compared to the untreated specimens. No differences were observed in the effect of the LASER conditions.