Influence of thermal exposure on microstructure and stress rupture property of a Re-containing Ni-based single crystal superalloy

In this study, the microstructural evolution and microstructure-property relationship of a Re-containing single crystal superalloy after long-term thermal exposure for up to 20,000 h at 900 degrees C have been investigated. The results showed that the microstructure of the experimental alloy significantly degraded after thermal exposure, including the coarsening of gamma' precipitates, the decrease of gamma' volume fraction and the morphology evolution of gamma' precipitates from cubic to spherical. The magnitude of gamma/gamma' misfits decreased obviously and then remained stable. The rupture life of the alloy at 900 degrees C/330 MPa dropped dramatically after thermal exposure for 2000 h, which was mainly caused by the obvious reduction of gamma' volume fraction, the decreased magnitude of gamma/gamma' misfits and the coarsening of gamma' precipitates. The rupture life of the alloy decreased slowly from 2000 h to 20,000 h, although gamma' size continued to increase from 680 nm to 1648 nm. The primary reason for this period was the unchanged gamma' volume fraction and the lower magnitude of gamma/gamma' misfits.

Automated summary

The study revealed that long-term thermal exposure at 900 degrees C caused degradation of microstructure and significant reduction in rupture life of the alloy, attributed to changes in gamma' precipitates and misfits between gamma and gamma'.