Selective laser melting of low-content graphene nanoplatelets reinforced 316L austenitic stainless steel matrix: Strength enhancement without affecting ductility

Metal matrix composites reinforced by carbon nanostructured material are beneficial in achieving a balance between strength and ductility. However, achieving this balance in stainless steel through the selective laser melting (SLM) process remains a challenge. In this study, SLM is used to fabricate 316 L stainless steel matrix composites, which are reinforced with 0.1 wt.% single-layer graphene nanoplatelets (GNPs). The optimal process parameters are obtained by combining the analyses of the relative density and mechanical properties. The results show that the GNPs in the 316 L/GNPs composites are dispersed at the grain boundary, either parallel or at a certain angle to the grain boundary. Based on the tensile test, the ultimate tensile strength of the 316 L/GNPs composites is 738 MPa, which was 17.9 % higher than that of 316 L. Furthermore, both SLM-printed 316 L and 316 L/GNPs composites have an elongation of ∼38 %. The interaction between the GNPs and the molten pool, and the redistribution of the GNPs leads to the formation of a lamellar and relatively high-density distribution area of GNPs in the molten pool. The strengthening mechanism of 316 L/GNPs composites is also elucidated. These results provide insights into enhancing the combined strength-ductility property of other SLM-printed GNPs reinforced metal matrix systems.