Carbon nanotubes as a unique agent to fabricate nanoceramic/metal composite powders for additive manufacturing

•A novel application of CNTs was exploited for preparing nanoceramic/metal powders.•The composite powders kept similar in shape, particle size, and distribution to raw metallic ones.•The Al2O3-coated metallic powders showed higher laser absorptivity than uncoated ones.•Al2O3 particles were uniformly dispersed and intimately contacted with the matrix after PBF.

Laser powder bed fusion (PBF) offers many technological opportunities for producing high-performance composite parts with tailored structures. However, fabrication of suitable composite powders possessing homogenous dispersion, good flowability, suitable particle size and distribution is a prerequisite and main challenge currently faced. In this study, a novel strategy was developed to prepare nanoceramic/metal powders by using acid-treated carbon nanotubes (ATCNTs) as an agent. In detail, a 3 wt% ATCNT/Al2O3 colloid, in which the negatively-charged ATCNTs were partially covered with positively-charged Al2O3 nanoparticles under electrostatic attraction, was obtained by heteroagglomeration; subsequently, the uncovered surface areas of ATCNTs were intimately bonded to the positively-charged MoTiAl powders during their mixing. This ATCNT bridging made individual Al2O3 uniformly wrap on the surface of MoTiAl without aggregation. The Al2O3-coated MoTiAl powders remained similar in shape, particle size, and distribution to uncoated ones, simultaneously showing higher laser absorptivity due to an increased surface roughness. The PBF-processed Al2O3-ATCNT/MoTiAl composite was dense, in which Al2O3 nanoparticles were homogenously dispersed and intimately contacted with MoTiAl, giving rise to an increase in the hardness of the matrix.

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