Direct energy deposition of ultrastrong WC-12Co cemented carbide: Fabrication, microstructure and compressive properties

Abstract

This study used the direct energy deposition (DED) of additive manufacturing (AM) process, which is capable of being fabricated in near-net shapes, to fabricate WC-12Co cemented carbide, and investigated its microstructure and compressive properties at room temperature. This study also examined the influence of scanning speed and hatch space on microstructural and mechanical properties using process parameter control. The initial WC-12Co (wt%) powder consisted of WC and ɑ-Co (fcc) phases. XRD analysis of WC-12Co, which was fabricated using the DED process, identified that it had WC and ɑ-Co (fcc) phase peaks as well as W2C and M12C (Co6W6C) phase peaks. The porosity of the DED-built WC-12Co specimens measured A: 3.91%, B: 18.61% and C: 14.28% according to each process condition. Among the three conditions, condition A, which had the highest volumetric energy density (VED), was confirmed to have the highest density. In all three materials, WC coarsening and WC decomposition was suspected to grain growth and consolidation. Furthermore, some secondary phases (W2C, M12C) were also observed. A compressive test measured maximum strength as A: 1.9 GPa, B: 1.4 GPa and C: 1.5 GPa, where condition A achieved the highest mechanical properties. All three materials had fracture behaviors where cracks propagated along pores. Cracks were relatively more apparent in condition B compared to the others. In the WC phase, both transgranular cracks and intergranular cracks were observed, and crack propagation was observed in the decomposition area as well.