Microstructural changes in alloy 625 during high temperature creep

Microstructural changes in the nickel-base alloy 625 during creep deformation have been investigated in the temperature range of 923 to 1148 K for durations from 30 to 31,800 h. Intermetallic phases such as γ″-phase and δ-phase have been found to precipitate extensively within the austenitic matrix under most of the test conditions. The γ″-phase was observed at 973 K and δ-phase was observed at all temperatures above 973 K. The morphology of the needle-shaped δ-phase was influenced by time and temperature of exposure and stress. An almost continuous decoration of M23C6 type carbides was observed on the grain boundaries.