Effects of temperature on microstructure and mechanical properties of IN718 reinforced by reduced graphene oxide through spark plasma sintering

The research of Nickel-based superalloys with excellent mechanical properties is of significance for aerospace. Here we report the effect of sintering temperature of 850 °C, 900 °C and 950 °C with the heating rate of 100 °C/min via spark plasma sintering (SPS) on Inconel 718 (IN718) superalloy reinforced with 0.25 wt. % reduced oxide graphene (RGO). The microstructures and mechanical properties of IN718-RGO composite were investigated by scanning electron microscopy (SEM) and MTS servo hydraulic testing machine, respectively. SEM results demonstrate that the RGO is almost uniformly distributed into the IN718 powders after 3D rock-milling for 8 h. The mechanical properties of the composite increase with increasing the sintering temperature. When the sintering temperature is 950 °C, a relative density of 92.5%, a microhardness of 375 Hv and an ultimate compressive strength of 1748.20 MPa after aging heat treatment was obtained for the IN718-0.25 wt. % RGO, respectively. The fracture mechanism of the composite changes from intergranular fracture to transgranular fracture with the sintering temperature increasing.