Effect of Cold Working on Creep Rupture Strength of Alloy617

The effect of cold working on the creep rupture strength of Alloy617 was investigated. The creep rupture tests were conducted at temperatures of 700 to 800°C, under stresses from 100 to 350 MPa. At high stress conditions, the creep rupture time of the non-pre-strained samples are similar to those of the pre-strained samples. On the other hand, at low stress conditions, the creep rupture time of the pre-strained samples are longer than those of the non-pre-strained samples. The amount of precipitates near the grain boundaries in the pre-strained sample is higher than that in the non-pre-strained sample. Weak regions such as PFZ and recrystallization grains in the non-pre-strained sample are formed in the early stage of creep compared to the pre-strained sample. At low stress conditions, the precipitates near the grain boundaries in the pre-strained sample play an effective role to pin the grain boundaries and they delay the formation of the weak regions resulting in extension to the creep rupture time.