Precipitation behaviour of γ′ phase in Alloy 693

• The alloy exhibits multi-modal distribution of γ′ precipitates formed in aged Alloy 693.
• The γ′ phase has been found contain up to 4 at% of Nb.
• Results have been explained on the basis of classical nucleation and growth models.

This paper reports the precipitation behaviour of γ′ phase in the newly developed Ni-base superalloy Alloy 693. Precipitation of γ′ particles is studied at different temperatures ranging from 800 °C to 950 °C under isothermal conditions for various time periods. Monomodal, bimodal and trimodal size distributions of γ′ precipitates have been observed depending on the temperature of annealing and the cooling rates. These studies have been carried out using scanning and transmission electron microscopy. Results are compared with existing literature and explained on the basis of classical nucleation and growth theory.