One of the limitations of the L-PBF technology is the high surface roughness of the parts. The resulting surface roughness morphology is a combination of the layer-by-layer building strategy and a stochastic pattern of spherical particles partially adhered to the surface. This stochastic pattern is composed by partially melted powder particles due to the heat transfer between the melt-pool and the powder particles at the part boundary. In this study, an experimental setup was designed to analyze the influence of the heat transfer of the L-PBF process on the adhered particles on the surface. Thus, the test parts consist on vertical walls distributed at different distances, from 0.2 mm to 5 mm, in order to promote different thermal gradients between surfaces. The manufacturing process was monitored using an IR camera, in order to find the relationship between the heat transfer and the mechanism of adhesion of particles. Moreover, the morphology of the resulting surface roughness of the parts was also analyzed. The results show a correlation between the temperature gradients and the number of adhered particles on the surfaces.

One of the factors that most affects surface roughness is the angle of incidence of the laser with respect to the platform, which varies across the platform. However, to make the L-PBF process a competitive technology, several parts must be manufactured on the same platform, using maximum building volume. Nevertheless, due to this angle of incidence, even if identical parameters and geometries are used, the surface finish of the parts varies considerably depending on the positioning of the part on the platform. Throughout this work, the effect that this angle of incidence has on the surface of parts manufactured in the different positions of the platform is presented. For this purpose, first the angle of incidence on the whole platform was determined. Then, based on these results, the distortion of the melt pool was analyzed analytically, with the aim of relating the poor surface finish, seen by different technologies such as infinite focus microscope or SEM, with the distortion of the melt pool generated by the angle of incidence.

The quality of the powder is a key aspect in the Laser Powder Bed Fusion (PBF-LB/M) process to guarantee manufacturability and quality of the manufactured parts. However, the powder is reused several times and its quality changes during the manufacture process, which affects the quality of the manufactured parts. Throughout this article, the powder and the final part properties will be studied during 25 manufacturing process. Specifically, morphology, granulometry and flowability of the powder were studied, and these results were related with the roughness and the porosity of the manufactured parts. Thanks to this research, it was found that the size of the particles increases when the powder is reused. And this directly affects the flowability of the powder which increases. Furthermore, it has also been shown that this increase in particle size distribution causes an increase in the porosity and roughness of the manufactured parts.