Process Characterization and Analysis of Ceramic Powder Bed Fusion

Powder Bed Fusion (PBF) of ceramics is often limited because of the low absorptance of ceramic powders and lack of process understanding. These challenges have been addressed using customized ceramic powders to increase absorptance and two process characterization techniques. The starting powder is made of a mix of granules and pure alumina powder. The granules are made of alumina, to which an oxide dopant is added to increase absorptance. The comparison of the performance of different granules and different process parameters is extremely complex because of the large number of influencing factors. Two methods for characterizing and analyzing the process of PBF are implemented: the first allows to analyze the reflectance of the laser during the melting of a single track using an integrating sphere; the second one is a setup to build clear imaging of the process using a high-speed camera and an external laser illumination. The absorptance behavior of the laser power during the melting of a single track is proven to be a highly non-linear and dynamic process. The results showed that manganese oxide dopant delivers higher and more stable absorptance with IR laser, compared to hematite-doped powder. The high-speed camera videos are recorded using an external blue laser illumination. The result is that clear pictures and videos of the melt-pool could be taken and automatically analysed with an image processing software. Several phenomena related to powder and melt-pool dynamics, such as change of melt-pool shape and dimension over time and powder denudation, could be observed.