Effect of cooling rates from partial solution temperature and aging on γ' precipitation in IN792 superalloy.

One of the important factors affecting the microstructure of Ni base superalloys is the cooling rate from partial solution temperature; therefore, the prime purpose of the present research is to investigate the effects of this factor on some microstructural features of superalloy IN792. The results showed that by increasing the cooling rate from 5 to 160°C min^-1 after partial solution treatment at 1120°C for 2 h, the size and volume fraction of primary γ' decreased, but during the subsequent aging the volume fraction of secondary γ' increased initially exponentially and later linearly. When high cooling rates >90°C min^-1 were applied, the formation of secondary γ' was totally suppressed. However, after aging at 845°C for a period of 24 h, the amount of secondary γ'. increased with a decelerating rate up to 60°C min^-1 and then with a linear rate up to 160°C min^-1 The later observation has not been reported elsewhere. [ABSTRACT FROM AUTHOR]