Comparison of microstructural stability of IN939 superalloy with two different manufacturing routes during long-time aging

Microstructural stability of IN939 superalloy with two different manufacturing routes was investigated during long-term aging at elevated temperatures by light optical microscope (OM) and scanning electron microscope (SEM) equipped with an EDS system. The results show that the coarsening behavior of γ′ particles is primarily impacted by the initial heat treatment conditions, and the ffect of the prior manufacturing route (casting or hot forming) is found to be insignificant, if any, on the γ′ particles coarsening kinetics. In the temperature range of 790–827 °C, IN939 cast/wrought-HT2 alloys have more microstructural stability, while in the temperature range of 827–910 °C, the initial heat treatment marked as HT1 provides more stable microstructure for the cast or wrought IN939 superalloy.