Laser powder bed fusion of functionally graded bi-materials: Role of VC on functionalizing AISI H13 tool steel

This study investigates the feasibility of fabricating defect-free functionally graded bimaterials (FGMs) with enhanced wear resistance via incorporation of vanadium carbide (VC) into H13 tool steel. Three distinct composite powders containing 1, 3, and 5wt.%VC were prepared through ball-milling and subjected to laser powder bed fusion (LPBF) process to print different composites on top of monolithic H13 in a wide range of process parameters. Almost fully-dense parts were achieved (maximum of 99.8, 99.8, and 99.5% for 1, 3 and 5wt.%VC composite systems, respectively); however, the increase in VC content narrowed down the processability window range from 60 J/mm3 for 1, and 3wt.%VC systems to 30 J/mm3 for 5wt.%VC system. The mechanical properties of optimum samples were characterized through microhardness, nanohardness, and wear tests. The incorporation of VC significantly improved the mechanical properties, 17-40% in microhardness, 10-40% in nanohardness, and 20-53% in wear resistance. The underlying reasons behind such an improvement were correlated to the dissolution of VC during the heating stage of the LPBF process and the formation of (V+C)-supersaturated solid solution in large extents as a result of extremely high cooling rates. This study introduces LPBF-processed FGMs as promising candidates for applications in which wear resistance is paramount.