Abstract: This article studies carbides and their reactions in nickel-base superalloy powders prepared by rapid solidification and the hot isostatic pressed (HIPed) alloy. With the pre-treated temperature rising, the segregation of alloy elements in the powders reduces, but MC carbides in the interdendritic region still exist at elevated temperatures. As a result, there are more Ti and Zr at this area. Blocky and petal-like MC carbides distribute in the interdendritic region of the initial powders. During the pre-heat treatment the blocky carbides decompose, and M₂₃C₆ and M₆C precipitate in the interdendritic region; however, the petal-like carbides can remain stable at higher temperatures. Carbides in the interdendritic region of the HIPed alloy are composed of blocky M₆C and MC and petal-like MC carbides, but deformation and recrystallization can induce the MC carbides to decompose.