Microstructure evolution, mechanical response and underlying thermodynamic mechanism of multi-phase strengthening WC/Inconel 718 composites using selective laser melting

For further understanding the underlying relations of microstructure evolution on mechanical properties of Inconel 718 composites reinforced by WC particles using selective laser melting (SLM), the influence of laser scanning speed on microstructure growth, evolution mechanism and mechanical properties was analyzed combining with experiments and mesoscopic simulations. The obtained results apparently reveal that the Ni2W4C primary dendrites exhibit with a reduced trunk length as well as the decreasing length and spacing of dendrite arms following an increasing scanning speed according to the combining analysis of X-ray diffraction spectrum and EDS, due to the significant reduction of operating temperature and the resultantly weak atoms diffusion rate and thermodynamic driving force of dendrite growth. Meanwhile, the (Nb, M)C carbides (M representing Ni, Cr, W, Fe, Ti) generated in γ-Ni matrix are inversely refined as elevating the laser scanning speed. Both the experimental microhardness and ultimate tensile strength of SLM-processed WC/Inconel 718 composite is, therefore, evidently enhanced with a slight reduction of elongation as successively increasing the scanning speed, attributing to the combined strengthening effects of refined multi-phase of Ni2W4C primary dendrite and granular (Nb, M)C carbides. Furthermore, the underlying evolution mechanism of composite microstructure with variable processing conditions is discussed.