Microstructure evolution behavior in electroslag remelting ingot of GH3536 alloy
Cooling conditions at different parts of the ingot is obviously different due to the solidification process of superalloy ingot with external preferential cooling.When the ingot size increases,the segregation of elements inside the ingot increases and generates coarse precipitated phases.To properly control the carbide distribution in ESR in-gots of GH3536 alloy and provide a theoretical basis for the development of ingot size casting,elemental segregation and evolution of carbides at different parts of ingot were investigated.Combined with actual industrial production,the zonal melting liquid metal cooling experiments and finite element numerical simulation MeltFlow-ESR were adopted under laboratory conditions to study the relationship between cooling rate and carbide morphology and sec-ondary dendrite spacing.The results indicate that the segregation of Mo,W and Cr elements during the solidifica-tion process is an important reason for carbide formation.With the increase of cooling rate,the secondary dendrite spacing and carbide phase area fraction both decrease,and the lower cooling rate increases the dendrite spacing,which is easy to form the composite carbide of M6C/M23C6.The primary dendrite spacing is λ1=396.78 G-0.5Rc-0 25 positively proportional related to the cooling rate Rc and the secondary dendrite spacing is λ2=102.74Rc-0 36 expo-nential related to the cooling rate.Comparison of industrial ingot casting and actual simulation results has revealed that the obtained numerical simulation results correspond well with the experimental results.It is further found that the melting rate of 230 kg/h is conducive to obtaining a uniform and dense solidification microstructure.
nickel-base superalloycomposite carbidecooling ratesolidification and segregationfinite element modeling
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