Process characterization and analysis of ceramic powder bed fusion

Abstract

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 through a co-development of customized ceramic powders and laser process capabilities. The starting powder is made of a mix of pure alumina powder and alumina granules, to which a metal oxide dopant is added to increase absorptance. The performance of different granules and process parameters depends on a large number of influencing factors. In this study, two methods for characterizing and analyzing the PBF process are presented and used to assess which dopant is the most suitable for the process. The first method allows one to analyze the absorptance of the laser during the melting of a single track using an integrating sphere. The second one relies on in-situ video imaging using a high-speed camera and an external laser illumination. The absorption behavior of the laser power during the melting of both single tracks and full layers is proven to be a non-linear and extremely dynamic process. While for a single track, the manganese oxide doped powder delivers higher and more stable absorptance. When a full layer is analyzed, iron oxide-doped powder is leading to higher absorptance and a larger melt pool. Both dopants allow the generation of a stable melt-pool, which would be impossible with granules made of pure alumina. In addition, the present study sheds light on several phenomena related to powder and melt-pool dynamics, such as the change of melt-pool shape and dimension over time and powder denudation effects.

Operando tomographic microscopy during laser-based powder bed fusion

“…For lower energy densities, the molten phase front remains in contact with the powder and for very low power the laser interacts directly with the powder (Supplementary Movies 1 and 2 for 3.35 W and 4.3 W). A similar effect was observed by Florio et al 59 using a high speed camera. Here, the energy density was varied by changing laser scanning speed, while keeping a constant laser power.…”

“…The typically used laser scanning speeds during LPBF of ceramics are in range from 1 to 100 mm/s 10,15,19,59 . For this range, the achievable tomogram rate is already compatible with typical laser velocities for ceramics, as for instance for 10 mm/s laser scanning speed and acquisition with 1000 tps, the laser spot would move by 10 µm during acquisition of one tomogram.…”

3D Printing of Bioinert Oxide Ceramics for Medical Applications

“…The use of PBF processes is limited for ceramics, because most ceramic powders have low absorptance [43]. However, some authors have worked in this area; for example, Juste et al, who obtained oxide ceramic parts with the SLM technology [44].…”

Advances and challenges in direct additive manufacturing of dense ceramic oxides

“…Scope of this review for the dAM of ceramic oxides. Image sources from [24][25][26][27][28][29][30][31][32][33][34][35]. Adapted from [24], with permission from Springer Nature.…”

“…Consequently, high relative density up to 99.6% can be achieved for r-GO doped ceramics at lower laser energy input, as compared to the carbon-doped ones. Other than carbon-based materials, Pfeiffer et al [65,66] and Florio et al [26,30] reported an absorption enhancement by incorporating colored oxide nanoparticles into raw Al 2 O 3 powders, such as Fe 2 O 3 and MnO 2 . They achieved an absorption rate of 90%, leading to a relative density exceeding 98% for the as-printed components.…”