Comparative analysis of mechanical properties and corrosion resistance of Co25Cr5Mo5W biomedical alloys fabricated by LPBF and CAST techniques

This study systematically investigates the mechanical properties and corrosion resistance of Co25Cr5Mo5W dental alloys fabricated via laser powder bed fusion (LPBF) (specimens named as-built) versus conventional casting (CAST) (specimens named as-cast). The as-built alloys exhibit a γ–FCC–dominated microstructure featuring a three-dimensional network of cellular subgrains, stacking faults (SFs), and limited ε-martensite laths, whereas the as-cast counterparts display coarse dendritic grains, a γ+ε dual-phase structure, and σ-phase precipitates. The as-built alloys demonstrate superior mechanical properties through strengthening from the three-dimensional network and enhanced ductility resulting from the dominant FCC matrix. Electrochemical analyses reveal that the as-built alloys also exhibit improved corrosion resistance, characterized by a lower corrosion current density and higher passive film stability. This enhancement is due to the homogeneous γ-FCC matrix and the absence of micron-scale precipitates. The ultra-fast cooling in LPBF suppresses the formation of micron-scale precipitation and inhibits the FCC to HCP phase transformation, achieving an optimal balance of strength, ductility, and corrosion resistance. These findings demonstrate that LPBF overcomes the inherent limitations of casting in defect and phase control, providing critical insights for developing patient-specific biomedical implants with extended service life. Furthermore, this work elucidates the microstructural optimization mechanisms of LPBF versus CAST Co25Cr5Mo5W alloys through advanced characterization, advancing the application of additive manufacturing in precision dental devices.