Study On Microstructure,Properties And Strengthening Of Inconel 718 Alloy Fabricated By Selective Laser Melting

Inconel718 nickel-based alloy has been widely used in the hot end parts of aeroengines due to its advantages of easy processing,good mechanical properties,high temperature creep and high temperature oxidation resistance.Although it has many outstanding advantages,the traditional manufacturing process of Inconel 718 nickel base alloy components is complex and the production cycle is long,the forming difficulty of complex forgings,all of which limit it to carry out more careful precision machining and modeling design.Selective Laser Melting?SLM?,as a new type of additive manufacturing technology,has advantages such as flexible process,complex structural parts that can be molded,and integration of material preparation and part molding,which is more satisfying for the design of hot end components of aero engines demand.This article takes Inconel 718 high temperature nickel-based alloy as the research object.The sample is prepared by Selective Laser Melting,and heat treatment and Laser Shock Peening are carried out.Metallography,SEM,EDS,XRD,hardness and residual stress of the samples before and after heat treatment and Laser Shock Peening were analyzed.The microstructure,hardness and residual stress of the material before and after heat treatment and Laser Shock Peening were discussed.The research results show that there are obvious weld bead structures on the surface of Inconel718 nickel-based alloy.The surface of Inconel 718 Alloy has serious inhomogeneity,with a large number of columnar crystals and fine dendrites.After double aging,the columnar and fine dendrites of Inconel 718 nickel base alloy changed into massive crystals,the weld bead structure disappeared and the surface hardness of the alloy increased significantly.With the increase of solution temperature,the surface of Inconel718 nickel-based alloy shows obvious refinement characteristics,typical columnar crystals,dendrites,intermetallic compounds and precipitation hardening phases?such as Cr-Fe-Mo-Ni,FeNi and Ni₈Nb Etc.?disappeared.After950?solution treatment plus double aging treatment,the fine and uniform?phase in the grains and??near the grain boundaries play an important role in relatively increasing the hardness of the alloy.When 1050?solution plus double aging treatment is adopted,the microstructure of the sample is more uniform,the hardness reaches the highest value,and the residual stress distribution is reasonable.After laser shock peening,the Z-Y surface structure of the alloy has a certain grain accumulation phenomenon.In the original and double ageing samples,the impact zone is obvious.While 950?solution plus double aging and 1050?solution plus double aging are used,the boundary of impact zone is not significant enough.However,Laser Shock Peening is helpful to improve the hardness of the specimen near the surface?the depth direction of the Z-Y surface?.The hardness of the alloy near the surface is improved significantly in the original and double aging treatment specimens.This is closely related to the incompact structure of this alloy and the effect of Laser Shock Peening.In addition,the residual stress of the original and the double aging samples are changed from tensile to compressive.When the processes of 950?solution plus double aging and 1050?solution plus double aging are used,the extreme value of the residual stress of the pattern increases,which shows that laser shock peening has a significant influence on the improvement of it.