Support-free laser-based powder bed fusion of metals using pulsed exposure strategies

Abstract

Several studies demonstrate the potential of pulsed exposure strategies for improving spatial accuracy, surface quality, and manufacturability of low-angle overhangs in laser-based powder bed fusion of metals. In this paper, those fundamental potentials are transferred to the support-free manufacturing of heat exchanger structures with partial horizontal overhangs made of Ti6Al4V. The pulsed exposure with pulse repetition rates of 20 kHz and pulse duration of 25 µs enabled the support-free manufacturing of these complex structures with densities of more than 99%. A comparison of the Archimedean density determination with optical density determination using micrographs indicate permeability of the specimens below an applied volume energy density of 30 J/mm3 due to open porosity. Furthermore, the pulsed manufactured structures show an improved flow behavior within the heat exchanger compared to specimens manufactured with continuous exposure strategies.