Effect Of Surface Treatment On Properties Of Traditional Casting And 3D Printing Inconel 718 Alloy

Inconel 718 alloy has excellent comprehensive service performance and is widely used in industrial production,aerospace and other fields.With the continuous development of aviation technology,more complex geometric structures and more excellent comprehensive performance requirements are put forward for the parts of key parts.The traditional processing technology can not meet the use requirements.Therefore,Inconel 718 alloy was prepared by 3D laser printing technology,and the effects of forming process on the mechanical properties,wear resistance and corrosion resistance of the alloy were investigated.The surface strengthening treatment of traditional casting and 3D printing Inconel 718 alloy was carried out by plasma enhanced magnetron sputtering technology,and the effect of surface treatment on the comprehensive properties of the alloy was investigated.The phase composition,microstructure,hardness,wear resistance and corrosion resistance of the sample surface were characterized by XRD,SEM,EDS,nanoindentation,friction and wear tester,step tester and electrochemical workstation,respectively.Firstly,Inconel 718 alloy was prepared by 3D printing technology,and the effects of forming process on the microstructure,mechanical properties and corrosion resistance of the alloy were investigated.The results show that the alloys with different forming processes have the same phase composition.There are a large number of fine and dense Nb-rich precipitates on the surface of 3D 718 alloy,so its surface hardness is 6.05 GPa,which is 1.1 times that of the cast alloy.Due to the unclosed pores on the surface of the 3D printed alloy,the porosity is 2.88%,resulting in an elastic modulus of 0.97 times that of the cast alloy.The 3D 718 alloy exhibits excellent wear resistance,and its wear scar depth is 21.35μm,which is 0.62 times that of the cast alloy.In addition,the corrosion potential of 3D 718 alloy in 3.5%Na Cl solution is-411.50 mV,showing low corrosion resistance.Secondly,the surface of the two alloys was treated by ion nitriding technology to study the diffusion and precipitation mechanism of nitrogen atoms in nickel-based superalloys and their effects on the comprehensive properties of the alloys.The results show that nitrogen atoms diffuse inside the alloy and formγ_N phase,CrN phase and Fe_xN phase.The depth of nitrided layer is 2.13μm and 2.89μm,respectively.After nitriding treatment,the mechanical properties,wear resistance and corrosion resistance of the sample were significantly improved.Among them,the hardness of IN 718 and3D 718 samples increased to 14.68 GPa and 16.49 GPa respectively,the wear scar depth decreased to 2.13μm and 2.89μm respectively,and the corrosion potential increased to 6.7 mV and-80.90 mV respectively.Finally,the surface strengthening treatment of the two alloys was carried out by nitriding treatment and PEMS technology CrN_x composite plating process,and the effect of nitrogen flow rate on the phase composition and comprehensive properties of CrN_x film was investigated.The results show that with the increase of nitrogen flow rate,the film phase changes from Cr/Cr₂N phase to Cr₂N/CrN phase,and the film thickness increases with the increase of nitrogen flow rate.After composite treatment,the mechanical properties and corrosion resistance of the samples were significantly improved.Among them,the 3D 718 sample with Cr₂N/CrN film structure exhibits the highest surface hardness of 25.66 GPa,which is about 4 times that of the untreated sample.The IN 718 alloy with Cr/Cr₂N film structure has the highest corrosion potential of 147.3 mV,showing excellent corrosion resistance.