From raw elements to 3D samples: An economical route for Co-Cr-Mo alloy fabrication

This study explores an efficient and feasible method for production of non-commercial Co-Cr-Mo powder feedstock for Laser Powder Bed Fusion (LPBF), employing mechanical alloying (MA) with following thermal treatment. Elemental Co, Cr, and Mo powders were subjected to MA to create a powder nanostructured composite. Initially, the mechanically alloyed powder had a mixed-phase state, with ε-phase as the main one (about 95 wt%) and impurities of Cr ₂O ₃ . However, an additional 1.5-hour of isothermal annealing at 400 °C successfully reduced the Cr ₂O ₃ impurities and caused oxygen content to decrease, indicating a reduction in residual oxygen in the powder. This annealing process activated diffusion and induced relaxation of residual stresses, evidenced by decreased lattice microstrains: 0.8% for the Co-phase, 0.2% for both the Cr-phase and Mo-phase. Powder subjected to the thermal treatment was then utilized in LPBF to create bulk Co-Cr-Mo samples. The formed samples showed a typical LPBF microstructure represented by uniaxial cells and dendrites, with the distance between these structures not exceeding 3 µm. The samples showed homogenous elemental distribution, mixed-phase composition, and oxygen concentration not exceeding 5 wt%. In terms of mechanical properties, the LPBF samples exhibited a microhardness value of 4300 ± 200 MPa, ductility of 0.85, and yield strength of 1.4·10 ³ MPa. Our method yields results comparable to those obtained from commercially spherical powder, indicating that our cost-effective approach does not sacrifice product quality. It represents a substantial cost reduction, approximately 4.5 times lower than that of commercial spherical powder, thereby highlighting the economic efficiency of our powder feedstock preparation for LPBF. Our findings underscore the potential of mechanically alloyed and thermally treated powder in LPBF. This worthwhile and efficient method of preparation powder feedstock breaks ground for more comprehensive facilities in 3D printing, cut down on cost of production with maintaining the high-quality output.