Penetration depth optimization for proper interlayer adhesion using near-infrared laser in a low-temperature process of PBF-LB/P

Abstract

The aim of this study is to discuss the influence of the optical properties of powder bed such as penetration depth, on the depth of fusion and proper interlayer adhesion. A low-temperature process of PBF-LB/P, in which the underlying layer was solid, was performed to gain insight into optimizing the optical properties of this process. The penetration depth was widely adjusted using near-infrared laser (wavelength 1.06 μm), which has high transmittance through most polymers, and by adding an optical absorbing agent to PA12 powder. To investigate the relationship between the penetration depth and depth of fusion when a powder bed is formed on top of the underlying layer, the depth of fusion at each penetration depth was estimated based on microstructural observations and a thermal analysis of the built specimens. The results showed a positive correlation between the penetration depth and depth of fusion when compared with the unified volumetric energy of the laser. The influence of the penetration depth and/or depth of fusion on interlayer adhesion, as well as the part resolution in the stacking direction, were discussed. The interlayer adhesion strength was evaluated from a tensile test in the stacking direction of specimens prepared using different penetration depths. The results demonstrated that the interlayer adhesion increased with increasing the penetration depth and that it was saturated at a certain penetration depth. Moreover, the part resolution simply tended to decrease with increasing the penetration depth. Therefore, it was shown that optimization can be realized by determining the penetration depth at which interlaminar adhesion is saturated.