A Study on the Improvement of High Temperature LCF Properties by Aging Treatment in Nb-A286 superalloy

摘要

The effects of growth of the gamma' and eta phase on the LCF in Nb-A286 superalloy are investigated by fatigues test, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The change of precipitates morphology, amount of phase and control of size are also discussed. Under the continuous low cycle fatigue, fatigue life is increased with increasing gamma' size and amount of eta phase. In the investigation of a fracture surface after low cycle fatigue test, fracture mode is changed from intergranular fracture mode to transgranular fracture mode with increasing gamma' size and amount of eta phase. It is changed from planar slip to bowing dislocation with increasing gamma' size. Slip induced cavitation by local stress concentration due to planar slip impinged on the grain boundary is retarded by a larger precipitation than that of unaged sample. Therefore, fatigue life is increased with gamma' size and amount of eta phase. These results will be applied to the development of a new alloy for the improvement of fatigue life.