Effect of Cooling Rate on Microstructural Development in Alloy 718

Abstract

A variety of cast pyrometR 718 alloy microstructures result from processing of different diameters of industrial scale ingots for producing superalloy forgings used in aircraft turbine engine applications. The hot workability of these cast alloys will significantly depend on the cast microstructure. The current study is focussed on understanding the evolution of the cast microstructure during Vacuum Arc Remelting (VAR) of 718 superalloy as it relates to secondary dendrite arm spacing, second phase evolution and distribution during solidification. The variation microstructure is related to different cooling rates encountered in superalloy production. The effect of cast structure on homogenization and hot working is also discussed.