Effects of Plasma Spheroidization Treatment on the Characteristics of MoSiBTiC Powders Fabricated by Freeze-Dry Pulsated Orifice Ejection Method

Abstract

Freeze-dry pulsated orifice ejection method (FD-POEM) is a promising approach of fabricating spherical refractory alloy or composite powders for laser powder bed fusion (L-PBF). However, due to the weak particle strength induced by their intrinsic pore characters, the FD-POEM powders were likely crushed during the powder recoating process. Taking MoSiBTiC alloys as an example, in this work, plasma spheroidization (PS) treatment was utilized to strengthen the FD-POEM powders. The MoSiBTiC powders were completely melted and rapidly solidified during PS, leading to the evolution of mesh-pore to a fully dense structure. Correspondingly, the PS powders displayed an increased sphericity of 0.98, while showing a significantly decreased particle size of 53.1 µm. Moreover, the laser absorptivity of PS powder was reduced because of the decreased multiple reflections via the smooth powder surface. Microstructure evaluations illustrated that the PS MoSiBTiC powders mainly consisted of the elemental (Ti, B, and C)-supersaturated Mo phase, as well as small amounts of Mo 5 SiB 2 , TiC, and Mo 2 B, indicating the occurrence of in-situ alloying during PS. Furthermore, the internal and inter-particle microstructures of PS powders were highly homogeneous, attributing to the uniformly dispersed elemental powders of FD-POEM powders. The results of this work suggest that the combination of FD-POEM and PS is an effective approach of fabricating refractory powders for L-PBF.