Abstract
Electron beam smelting layered solidification technology is applied to prepare a nickel-based superalloy for turbine disks with service temperature up to 850 ℃. The microstructures, segregation and homogenization behavior were investigated. The results show that there is a cellular crystal structure with a width of 1.5 mm between the layers, and the dendritic structure is observed within the layers. The average secondary dendrite arming spacing is 28.6 um, which attributed to higher temperature of molten pool and faster cooling rate. After electron beam smelting layered solidification technology, the macrosegregation is eliminated, and the microsegregation is weakened. The average temperature on the molten pool surface during electron beam smelting is 1813 K according to evaporation rates of Ni. The effect of homogenization treatment on the microstructures and microsegregation evolution was discussed. Based two diffusion models, the diffusion coefficient of Nb and W at 1190 °C are caculated as 7.365 × 10 -16 m 2 /s and 5.805 × 10 -16 m 2 /s, respectively. • The secondary dendrite arm spacing and the size of γ′ phase prepared by electron beam smelting layered solidification are significantly reduced compared with alloy prepared by VIM plus VAR. • Electron beam smelting layered solidification technology can eliminate macrosegregation of ingots and reduce microsegregation. The segregation coefficient of W prepared by EBS-LST is 11.5% lower than that prepared by VIM plus VAR; and the segregation coefficient of Nb prepared by EBS-LST is 5.4% higher than that prepared by VIM plus VAR. • The average temperature of the melt is calculated as 1813 K according to the evaporation rate of Ni. • The diffusion coefficients of Nb and W in GH4975 alloy are calculated base on the diffusion models, whose values are 7.365 × 10 -16 m 2 /s and 5.805 × 10 -16 m 2 /s, respectively at 1190 °C.
Published Version
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