Defects such as pores and cracks remain a critical barrier to the laser powder bed fusion (L-PBF) of Mo and other refractory metals, owing to their high melting point, oxygen sensitivity, and the steep thermal gradients involved in the process. To overcome this challenge, this study proposes a TiC nanoparticle surface-decoration strategy achieved via a novel freeze-drying approach, enabling the fabrication of a near-defect-free Mo-TiC composite. The incorporation of TiC nanoparticles significantly suppresses the formation of pores and cracks and promotes the in-situ formation of unique Ti-rich core–Mo₂C shell precipitates, thereby inhibiting Mo oxide formation through effective oxygen scavenging. Enhanced crack resistance is closely associated with grain refinement and efficient oxygen impurity control. Consequently, the composite exhibited an increase in hardness, resulting from the synergistic contributions of solid-solution strengthening, grain-boundary strengthening, dislocation strengthening, and precipitation strengthening. This work provides valuable insights and a feasible strategy for inhibiting cracking in refractory metals processed by L-PBF. • Proposes a novel in-situ alloying strategy that introduces Ti and C elements to enhance the crack resistance of additively manufactured Mo. • Achieves a significant reduction in pores and cracks in Mo fabricated by laser powder bed fusion, enabled by dense microstructures formed in-situ with unique Ti-rich core–Mo₂C shell precipitates that suppress Mo oxide formation. • Reveals a crack elimination mechanism attributed to grain refinement and efficient removal of oxygen impurities, providing guidance for crack-free refractory alloy fabrication. • Enhances the microhardness of the Mo-based alloy through combined solid-solution strengthening, grain-boundary strengthening, dislocation strengthening, and precipitation strengthening.
Guo et al. (Sun,) studied this question.