Formation Process of Microstructure in Laser Powder Bed Fusion with WC Cemented Carbide Powder

Abstract

In this paper, the microstructure formation process of WC cemented carbide manufactured by Laser Powder Bed Fusion (LPBF) was investigated with WC/25 wt%Co agglomerated and sintered powder. The internal structure of the as-built cemented carbide specimen was categorized into two regions. The first region included many pores and a unique microstructure which was not observed from the samples fabricated with conventional manufacturing methods. In this region, W₂C and W₃Co₃C were formed due to a WC decomposition and an evaporation of graphite and Co during laser irradiation. On the other hand, the second region showed the similar microstructure to the conventional method. The microstructure of the first region revealed that the powder was completely melted during a laser scanning process. The precipitation process of W₂C, W₃Co₃C, and Graphite phase was considered with calculated liquidus projection of a C-Co-W ternary phase diagram.