Microstructure characteristics and surface oxidation behaviour of SLM WC/IN718 composite

In this work, WC/Inconel 718 composite was fabricated by selective laser melting (SLM) the IN718 superalloy powders decorated with surface embedded WC powders. Also, the composite was heat-treated by a designed double-aging regime for microstructure tuning. The resulting microstructure and surface oxidation behaviour of the as-printed and the heat-treated composites were studied. The results revealed that the homogeneous microstructure was obtained, and the obvious weld beads structure with fine dendrites was detected on the surface in the SLM composite. After the double-aging heat treatment, the matrix showed a confined growth from 21.81 to 26.14 μm and the weld bead structure disappeared. XRD and EBSD analysis confirmed the formation of γ, γ′, γ′′, WC, (Nb,M)C, δ and Laves phase in the composites before and after heat-treatment. The high-density GND accommodated the strain incompatibility and the internal residual stress in different constituents. Furthermore, the underlying mechanism of oxidation behaviour was discussed.