Investigation On Additive Manufacturing Technology,Microstructure And Properties Of TC4-IN718 Gradient Materials

With the development of the manufacturing industry,the requirements for the service conditions of materials are getting higher and higher.On some occasions,the traditional single homogeneous material is not enough to meet the existing complex requirements.TC4 has the advantages of high specific strength,good fatigue resistance,good corrosion resistance,etc.It is widely used in national defense,marine,aerospace,and other fields,but its high-temperature performance and wear resistance are poor;Inconel 718 is at room temperature and high temperature.（<700℃）has excellent mechanical properties,good corrosion resistance,and oxidation resistance,and is widely used in high-temperature structural parts in the fields of aerospace,military industry,and energy,but its specific strength is low.Since the physical properties of TC4 and Inconel 718 are quite different,direct bonding of the two materials will bring inevitable cracking and delamination.Connecting TC4 and Inconel 718 in a gradient combination,replacing the abrupt interface with a gradient interface can reduce the stress concentration effect caused by the mismatch of physical properties,and prepare a TC4-Inconel718 functional gradient that meets both high-temperature resistance and lightweight.Material（Functionally graded material,FGM）,improves the performance and life of related components.In this paper,a gradient material was prepared by using selective laser melting（SLM）with a 10 wt%composition change as a composition change step to transition from pure TC4 to pure Inconel 718.The optimal process parameters at different alloy components were explored,the phase composition and phase change of different alloy components were analyzed to reveal the relationship between microstructure,phase composition,and mechanical properties.The corrosion resistance of the samples under high temperature corrosion environment was tested and analyzed.The results of the study show that the laser power density during printing needs to be gradually increased as the Inconel 718 content increases.The higher laser power and energy density can make the different powders fuse well after melting,while ensuring the sample forming quality.When the samples were transitioned from pure TC4 to pure Inconel 718,the phase composition changed asα+β→β-Ti+Ti₂Ni→Ti₂Ni+Ni Ti→γ+Ni₃Ti+Fe₂Ti→γ+Laves.The mechanical property test results showed that the hardness increased and then decreased with the increase of Inconel 718 content,and the peak hardness reached 873±30 HV.The corrosion resistance test results showed that the surface of TC4-Inconel 718 samples generated Ti O₂,Al₂O₃ and Cr₂O₃oxidation layers after 160 h at 680℃under the corrosion environment of molten salt.The corrosion resistance of the samples decreased with the increase of TC4 content.The high temperature corrosion resistance of TC4-Inconel 718 gradient functional material was lower than that of pure Inconel 718.