The Study Of Properties And Microstructure On Graphene/Inconel 718 Composites Prepared By 3D Printing

Graphene/Inconel 718 composites were firstly synthesized through ultrasonicated dispersion and selective laser melting,the as-deposited composites were subjected to solution treatment(ST),solution+aging standard heat treatment(SA)and direct aging treatment(DA).The microstructures of composites were observed by OM,XRD,SEM and Raman spectra method,and the mechanical and tribological properties were tested at room temperature.Effect of heat treatment on the microstructure and properties of graphene/Inconel 718 composites were investigated and the mechanism of graphene nanoplatelets(GNPs)reinforced Inconel718 alloy is revealed.The main conclusions are as follows:The as-deposited GNPs/Inconel 718 composites prepared by SLM method has excellent mechanical properties and tribological properties.The yield strength,ultimate tensile strength and vickers hardness of 1.0 wt.% GNPs/Inconel 718 composites are 42%,53% and 34% higher than those of pure material,and the friction coefficient and wear rate are 22% and 66.8% lower than those of pure material.The strengthening mechanism of GNPs reinforced Inconel 718 alloy were attributed to high-density dislocation will occur,lattice distortion at the interface,dendrites refinement,impede the dislocation motion,restrain crack propagation and Load transfer etc.The superior wear resistance of GNPs/Inconel 718 composites can be attributed to the conventional reinforcing mechanisms through GNPs and the in-situ formation of GNPs anti-wear protective layer on the sliding contact interface.Therefore,results in obvious lubrication effect.The recrystallization occurs when the GNPs/Inconel 718 composites are solution treated and the microstructure changes from small dendrites to equiaxed grains.Therefore,the ductility is increased.when the solution treatment temperature is low(940? and 980?),a few number of microgranular ? phases was precipitated.In the process of solution treatment,Carbid [Nb,Ti]C is formed by reaction of GNPs with Ti and Nb element due to the solution temperature is higher,carbides belongs to the hard brittle phase is prone to itself-cracking and cracking in the interface,which resulting in the occurrence of crack source.Thus,leads to the decrease of yield strength,ultimate tensile strength and vickers hardness of composite materials.Compared with the deposited GNPs/Inconel 718 composite,the yield strength,ultimate tensile strength and vickers hardness of the composite were decreased aftersolution composite are aging heat treatment.However,the ductility is increased.This is because forming carbides [Nb,Ti]C in solution treatment,the Nb and Ti elements in the composites are greatly reduced and there is not enough Nb element and Ti element to precipitate ??(Ni3(Al,Ti))and ??(Ni3Nb)strengthening phases.Thus,yield strength,ultimate tensile strength and vickers hardness of the composite were decreased.The properties test of GNPs/Inconel 718 composites after at 620? and 720?single aging and 720? +620? double aging shows that composite has the high yield strength,ultimate tensile strength and vickers hardness under 620 ? single aging condition.The yield strength,ultimate tensile strength and vickers hardness of0.25 wt.% GNPs/Inconel 718 composite were 1164 Mpa,1400MPa and 549 HV after620? single aging,which are 28%,10% and 28% higher than those as-deposited composites.Because the temperature of 620? single aging heat treatment is low,there is no Carbid [Nb,Ti]C is formed by reaction of GNPs with matrix and remain the Two-dimensional structure of GNPs.Thus,Strengthening is resulted by GNPs.Moreover,after the 620? single aging heat treatment,the composite precipitates ??and ?? strengthening phases,which strengthen composites by impeding dislocation motion.Therefore,the yield strength,ultimate tensile strength and vickers hardness of GNPs/Inconel 718 composite reached the maximum after 620? single aging heat treatment and the 620? single aging heat treatment process is the optimum.