Study On Crafts And Microstructure Properties Of GH4169 Superalloy By Plasma Arc Welding Additive Manufacturing

N718 is a precipitation-hardened nickel-based superalloy and consists of a bodycentered cubic(?”)phase and a face-centered cubic(?').It was developed by American International Nickel Company in 1959.On the basis of Inconel 718,China has done some improvement and developed to be GH4169.GH4169 melting usually adopts vacuum induction+vacuum consumable remelting(VIM + VAR)double or vacuum induction + electroslag remelting + vacuum consumable(VIM + ESR + VAR)triple combination.The superalloy has good weldability,oxidation resistance,fatigue resistance and organization stability.It is widely used in the aerospace field.In this paper,the GH4169 superalloy samples is prepared by plasma arc welding(PAW)melting deposition additive manufacturing method,and its forming process parameters,heat treatment process system research,microstructure changes are focused,and the influence of rolling conditions on the temperature and stress field are simulated in the forming process.Through this research,the research on the additive manufacturing process of GH4169 has been further in-depth,laying the foundation for the transition from the additive manufacturing of TIG welding to the additive manufacturing of PAW welding for the preparation of GH4169 alloy in the laboratory.In the forming process of additive manufacturing,the PAW method was used to ensure the quality of the cladding layer,and used infrared thermal imager to monitor the temperature of the track was below 150? to prevent the grain coarsening and heat cracks of GH4169.In the research process,we improved several main process parameters: deposition current,deposition speed,wire feed speed,and the interlayer temperature.The forming process of small current and large current with different heat input parameters was compared.It was found that the number of Laves phases precipitated in the formed sample with small heat input parameters is less than that of the high current value and the size is smaller.The GH4169 sample is more stable.In terms of heat treatment process,we compared the direct solution + double aging heat treatment process(SA)with homogenization + solution + double aging heat treatment process(HSA).It was found that the as-deposited structure is a columnar crystal that grows along building direction of the sample,and the precipitated phases include Laves phase,? phase,?' sub-reinforced phase and ?” strengthened phase,and MC carbide.The Laves brittle phases can be found by scanning electron microscopy(SEM),which damage the strength of GH4169.The purpose of heat treatment is to dissolve the Laves phase back to matrix,and precipitate the strengthening phase ?' and ?" phase,thereby improving the properties and stability of GH4169 superalloy.And we found that by using the SA treatment process,the Laves phases are less soluble.However,the HSA treatment process can dissolve most of the Laves phases into the matrix.In this heat treatment,the number of obtained Laves is very small and finely dispersed,but a certain amount of ? phase will be precipitated.In the aspect of PAW deposition-rolling composite additive manufacturing,the influence of the reduction on the temperature field and residual stress of PAW arc microcasting and forging was mainly discussed through numerical simulation.The results show that the chilling effect of the rolls can effectively change the temperature field in the rolling area.: the temperature in the rolling area can drop below 400? and rise to 500? at the exit because of internal energy produced by plastic deformation.The greater the rolling reduction,the greater the plastic strain of the weld bead.A larger reduction at a certain gunroller distance can make the residual stress smaller.