Improvement of powder fabrication for additive manufacturing using ultrafine bubbles

Freeze-dry pulsated orifice ejection method (FD-POEM) shows great potential in producing spherical refractory or multi-component alloy powders. However, addressing the dispersibility issue of high-concentration slurries is required to broaden the application scope of FD-POEM in additive manufacturing. To this end, this study proposes the use of ultrafine bubble (UFB) water as an economical additive to improve slurry dispersibility without introducing impurities. A refractory MoSiBTiC alloy with complex compositions was chosen as an example to demonstrate the effect of UFBs on the dispersibility of the slurry mixture and the morphology of the FD-POEM powders. The underlying mechanism of the improved slurry dispersibility was elucidated through calculations of repulsive forces. Consequently, the operational range for the FD-POEM process was significantly expanded from 10 to 20 % when using UFB water. In addition, the MoSiBTiC alloy build was fabricated via laser powder bed fusion (L-PBF) using FD-POEM-produced powders with UFB additives, exhibiting uniform dendrites and fine TiC nanoparticles distributed in the matrix. This study not only expands the potential applications of UFB water in powder fabrication but also paves the way for the processability of Mo-based parts with advanced microstructures by combining FD-POEM with L-PBF.