Laser additive manufacturing of pure molybdenum using freeze-dry pulsated orifice ejection method-produced powders

Abstract

Preparing appropriate initial powders is a key factor in using laser powder bed fusion (L-PBF) for high-performance refractory materials. In this study, we developed a novel technology, the freeze-dry pulsated orifice ejection method (FD-POEM), for producing spherical molybdenum powders with controllable particle size and distribution and good flowability without melting. The Mo powders, which had unique mesh-structures, exhibited higher laser absorptivity than the dense ones. Pure Mo builds were fabricated using L-PBF. Fine MoO2 particles were formed and uniformly distributed along the grain boundaries and inside the equiaxed grains. High-resolution transmission electron microscopy revealed an interfacial orientation correlation between Mo [1 -1 -1]//MoO2 [0–1 0] and Mo (1 1 0)//MoO2 (0–1 2). The Vickers hardness of the Mo build increased compared to that of pure Mo owing to grain refinement and the oxide-dispersion-strengthening effect of in-situ MoO2. This study provides the basis for powder fabrication using FD-POEM and the processability of Mo parts via L-PBF in ultrahigh-temperature applications.

Keywords

• Laser powder bed fusion (L-PBF)
• Freeze-dry pulsated orifice ejection method (FD-POEM)
• Molybdenum
• Oxide-dispersion-strengthening