Microstructural Characterization of Functionally Graded WC–17Co with an Innovative Design Manufactured by Laser Direct Energy Deposition (LDED) Technology

Abstract WC–Co is valued for its high hardness and wear resistance, but its limited toughness restricts broader applications. To address this, a unique architecture was designed where steel layers are sandwiched between WC–17Co regions to improve ductility by development of a functionally gradient structure. Laser direct energy deposition (LDED) technique as a relatively new additive manufacturing technology (AM) was employed to develop this design due to its precision and suitability for developing complex geometries. Because LDED operates on a layer-by-layer basis, it allows gradual compositional transitions, enabling the creation of a functionally graded material (FGM) that minimizes thermal mismatch and stress concentration. The resulting microstructure was examined using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD). For comparative purposes, all experiments were performed on a conventional (non-FGM) LDED-processed WC–17Co sample as well. The average porosity and grain size was smaller in FGM compared to the non-FGM sample. Substantial deviations in lattice parameter of WC for the FGM sample were observed compared to the non-FGM one and reported literature for conventionally-processed WC–17Co. XRD results revealed that the FGM sample exhibits a shift in detected peaks followed by reduced residual stress than the non-graded structure, thereby decreasing the likelihood of crack initiation. The measured crystallite sizes aligned well with previously published data. While FGM sample exhibited higher hardness than non-FGM, it should also be noted that detailed analysis of mechanical properties is not within the scope of this study. This is a preliminary study only focusing on microstructural characteristics, and results could be used to explain mechanical, thermal, and electrical properties of newly developed structures in future studies.