Study On Microstructure And Properties Of Plasma Rapid Forming TiC Reinforced Superalloy Matrix Composite

Plasma rapid forming technology can be used in the direct forming of complex metal prototypes or parts,the rapid forming of metal or gradient materials,and the surface repair of metal parts.It is a low cost direct rapid forming effective way of manufacturing metal structures.Inconel 718 is widely used because of its highest yield strength in superalloy in 650 ?,and good anti-fatigue,anti-oxidation,corrosion resistance and long-term stability of the organization.TiC is widely used as the reinforcement phase in the wear resistant composites because of high melting point,high elastic modulus,high hardness,good wear resistance and good thermal stability.In this paper,Inconel 718 powder,Inconel 718-23.5Ti-14.5 nickel coated graphite?wt.%?,Inconel 718-29.5Ti-20.5 nickel coated graphite?wt.%?and Inconel 718-37.5Ti-26.5 nickel coated graphite?wt.%?composite material mixed powder were used as raw materials.The high temperature wear-resistant composites were prepared by plasma melting deposition rapid forming technology,which were consisted of TiC high temperature wear-resistant enhancement phase,Inconel 718 superalloy substrate with y"-Ni₃Nb high temperature strengthening phase and the nickel base solid solution of alloying elements.XRD,OM,SEM,EDS were used to analyze the micro structure and phase composition of Inconel 718 samples and composites.The results showed that the plasma rapid forming Inconel 718 samples were composed of y"-Ni₃Nb high temperature enhancement phase and ?-?Ni,Fe?solid solution;and the composites were composed of TiC wear-resistant enhancement phase,y"-Ni₃Nb high temperature enhancement phase and y-?Ni,Fe?solid solution.The microstructure of the composites was small and dense,and the y"-Ni₃Nb is attached to the primary TiC phase,the primary TiC phase is gradually coated by ?"-Ni₃Nb.Influence of heat treatment on Inconel 718 samples and the composites were different.Solution and aging treatment improved the precipitation of ?"-Ni₃Nb on Inconel 718 sample,but the direct aging treatment did not.The two kinds of heat treatment process on the composites had different effects to the y"-Ni₃Nb phase,but all of them led to the coarsening of the microstructure and the continuous formation of precipitates.The microhardness of the composites was measured by microhardness tester.The results showed that the hardness of the composites increased with the increase of TiC content in the composition design.The pin-on-disk room temperature wear tester was used to measure the room temperature dry sliding wear property.The results showed that in the condition of room temperature dry sliding wear,wear resistance of Inconel 718 is poor,solution and aging treatment had limited benefit to the wear resistance.TiC played a key role in the wear resistance at room temperature of the composites,the wear resistance of the composites were increased with the content of TiC,the effects of two kinds of heat treatment processes on the microstructure of the composites were not favorable to the wear resistance of the composites at room temperature.The ball-on-disk high temperature wear tester was used to measure the high temperature dry sliding friction and wear properties.The results showed that in the condition of high temperature dry sliding wear,due to the interaction of oxidative wear and abrasive wear,the oxide film on the surface of Inconel 718 which was destroyed by the contact stress led to further oxidation and the phenomenon of oxide film spalling and transfer.The wear resistance of the composites were effectively improved due to the existence of TiC wear resistant phase,and the further oxidation of the composites was inhibit,compared to the Inconel 718 superalloy,the composites had a lower friction coefficient and wear rate.But high TiC content was not benefit to the load resistance of the composites,so with the combined action of appropriate TiC wear resistant phase and Inconel 718 superalloy substrate,the composite materials exhibited good high temperature wear resistance and the load-insensitivity.Among the three composites,the one prepared by Inconel 718-29.5Ti-20.5 nickel coated graphite?wt.%?powder had the best high temperature wear resistance,which should be used in the high temperature and strong wear condition under the condition of high contact stress.