THE INFLUENCE OF LASER POWER AND SCAN SPEED ON THE MICROSTRUCTURE, DISTORTIONS, AND MECHANICAL PROPERTIES IN THE L-PBF OF Ti-6Al-4V

Laser powder bed fusion (L-PBF) has gained a lot of interest for its ability to build complex geometries with freedom of design. The wrong choice of process parameters like laser power (P) and scan speed (v) can result in parts with low ductility, pores, and distortion. In the literature, the influence of P and v on the quality of the printed part in terms of porosity defects, distortion, and mechanical properties has been widely explored. However, to obtain functional parts without defects it is crucial to consider different aspects simultaneously. This paper aimed to fill the lack of knowledge in the literature about the combined effect of laser power and scan speed on microstructure and distortions and their influence on mechanical properties. In this frame, tensile tests, microstructural, density, and distortion measurements were carried out to study the effect of P and v on mechanical strength, ductility, density, and distortion for Ti-6Al-4V parts produced with L-PBF. Three levels of P and v were analyzed in a range of 340-380 W and 1400-1600 mm/s, respectively. From the experimental analysis, a big influence of P on the ultimate tensile strength (UTS) and density was observed. Ductility, instead, was more affected by the v. Overall, high P and v resulted in significant distortions due to the increase in thermal gradient and cooling rate. Furthermore, porosity acted as a stress-relieving factor, and as a consequence, samples with high porosity showed less distortion.