[T6] AM Beam Based Technologies

[15B-T6-08] Electron Beam Powder Bed Fusion of High-carbon Co–Cr–Mo Alloys for Industrial Applications

*K. Yamanaka¹, S. Aota¹, M. Mori², N. Sasaki¹, J. Adrien³, E. Maire³, D. Fabrègue³, A. Chiba¹ (1.Tohoku University, Japan, 2.National Institute of Technology, Sendai College, Japan, 3.INSA Lyon, France)

Keywords:additive manufacturing, electron beam powder bed fusion, solidification behavior, Co–Cr–Mo alloys, carbides

Co–Cr–Mo-based alloys have been used for biomedical applications due to their excellent corrosion resistance. In this study, using electron beam powder bed fusion additive manufacturing, we prepared Co–Cr–Mo alloys with carbon concentrations up to their eutectic composition (~2.5 mass%). The hardness of the as-built alloys increased linearly with the carbon concentrations, reaching HRC60 at 2.5 mass% C, while maintaining excellent corrosion resistance superior to that of high-carbon stainless steels. The as-built microstructures contained a fine carbide network, increasing the carbon concentration not only increased the carbide fraction but also changed the solidification behavior from cellular at low carbon concentrations to dendritic, and finally to eutectic. Quantitative X-ray tomography revealed that such a variation also affects gas pore behavior in the melt pool, significantly reducing porosity when a flat solid/liquid front existed upon solidification. The developed alloys are unattainable through conventional metal processing, opening new avenues for industrial applications.