Effect of heat treatment parameters on SLM-fabricated GNPs/IN718 composites: microstructural evolution and mechanical properties

This paper systematically investigated the effects of solution and solution aging treatments on the microstructure evolution and mechanical properties of selective laser melting (SLM) graphene nanoplatelets (GNPs)-reinforced Inconel 718 (IN718) composites. The selective orientation of the grains in the heat-treated SLMed GNPs/IN718 composites gradually disappeared, and the changes in the morphology and precipitation phases of the grains were systematically investigated. Results show that the solution treatment eliminated the dendritic and cellular crystal structure within the composite, while also producing a large number of white carbide particles. The mechanical properties of the composites decreased with increasing temperature after the solution treatment. Solution aging treatments eliminate elemental segregation, precipitate a large number of gamma ''-strengthened phases, and improve the materials' tensile strength and wear resistance. Notable changes were observed compared with the untreated specimens. The hardness and tensile strength exhibited respective increases of 26.4% and 1.5%. Conversely, the elongation was reduced by 14%. Moreover, the average coefficient of friction and weight loss dropped by 6.89% and 18.78%, respectively. In the friction test, GNPs act as a lubricating phase, resulting in a significant increase in the friction wear performance of the composite. The heat treatment process releases residual stresses within the composite and improves the internal anisotropy of the material. This work is expected to provide a potential pathway to obtaining attractive mechanical properties for nickel-based superalloy components.