Graphene-strengthened Inconel 625 Alloy Fabricated by Selective Laser Melting

Graphene has been widely used as a reinforcement phase in composites due to its excellent electrical, thermal and mechanical properties. In this study, graphene was modified by electroless nickel plating to obtain nickel-coated graphene (Ni-Gr), which was then introduced into spherical Inconel 625 powder by ball milling. Selective laser melting (SLM) was subsequently used to fabricate Inconel 625/Ni-Gr metal matrix composites containing different levels of Ni-Gr (0, 0.4 vol%, 1.0 vol%). The effects of Ni-Gr content on the microstructure, mechanical, wear and corrosion properties of Inconel 625/Ni-Gr composites were investigated. Noticeable grain refinement was observed at the addition of 0.4 vol% Ni-Gr. The micro-hardness of Inconel 625/Ni-Gr composites increased with increasing Ni-Gr content and registered 348.2 HV0.2 at the addition of 1.0 vol% Ni-Gr. However, the Inconel 625/0.4Ni-Gr composite attained the maximum tensile strength (927 MPa), yield strength (797 MPa) and elastic modulus (227 GPa), aside from exhibiting lower friction coefficients than Inconel 625 at room temperature. In addition, it displayed higher corrosion potential than Inconel 625 and lower corrosion current density than Inconel 625/1.0Ni-Gr. The addition of Ni-Gr clearly improves the micro-hardness, tensile strength, yield strength, wear and corrosion properties of Inconel 625 due to grain refinement, solid-solution strengthening and impediment to dislocation motion. And, this study has verified the feasibility of preparing Inconel 625/Ni-Gr composites by SLM.