Metal-additive manufacturing techniques, such as selective laser sintering (SLS), are increasingly utilized for new biomaterials, such as cobalt-chrome (Co-Cr). In this study, Co-Cr gas-atomized powders are used as charge materials for the SLS process. The aim is to understand the consolidation of Co-Cr alloy powder and characterization of samples sintered using SLS under various conditions. The results clearly suggest that besides the matrix phase, the second phase, which is attributed to pores and oxidation particles, is observed in the sintered specimens. The as-built samples exhibit completely different microstructural features compared with the casting or wrought products reported in the literature. The microstructure reveals melt pools, which represent the characteristics of the scanning direction, in particular, or of the SLS conditions, in general. It also exposes extremely fine grain sizes inside the melt pools, resulting in an enhancement in the hardness of the as-built products. Thus, the hardness values of the samples prepared by SLS under all parameter conditions used in this study are evidently higher than those of the casting products.

Abstract
1. Introduction
2. Experimental
    2.1. Material information and sintering parameters
    2.2. Phase and Microstructural characterization
    2.3. Hardness measurements
3. Results and discussion
4. Conclusions
Acknowledgments
References

• Dong-Wan Lee(School of Materials Science and Engineering, University of Ulsan)
• Minh-Thuyet Nguyen(School of Materials Science and Engineering, University of Ulsan, Hanoi University of Science and Technology)
• Jin-Chun Kim(School of Materials Science and Engineering, University of Ulsan) Corresponding author