Correlation between evolving microstructures and mechanical properties of served inconel 783 superalloys

Microstructures and mechanical properties of Inconel 783 superalloys, which were used as ultra-supercritical steam turbine bolts for different time, were systematically investigated. The results showed that the strength of the superalloys increased concomitantly with the service time, while the ductility and impact toughness exhibited successive degradation. Theoretical calculations regarding various strengthening mechanisms demonstrated that the strength increment was mainly due to the enhanced precipitate strengthening. Moreover, effects of multiscaled phases on the ductility were successfully analyzed with a modified model, which attributed the reduced ductility to the microscaled phases with high volume fraction. Besides, a relationship correlating the impact toughness with the evolving microstructures and yield strength was examined, which is consistent with the present experimental results, as well as those of other alloys in the literature. The result revealed that the toughness degradation was caused by the higher content and/or larger size of the second phase. This work was useful for performance enhancement and evaluation of the Inconel 783 superalloy.