Tian Sugui

Research on the creep fracture mechanism of FGH95 Ni-based superalloy

Abstract The creep fracture mechanism of FGH95 superalloy has been investigated by means of microstructure observation and creep behaviour measurement. Results show that, after solution treatment at 1150°C, the coarser γ′ precipitates distribute in the wider regions of previous particle boundaries. As the solution temperature increases to 1165°C, the grains grow in the alloy and carbide films precipitate along the grain boundaries. When the alloy is solution treated at 1160°C, the coarser γ′ phase in boundary regions is fully dissolved, and granular carbides precipitate along the grain boundaries, which may effectively restrain boundary sliding and hinder dislocation movements to improve the creep resistance of the alloy. During creep, the deformation feature of the alloy is that slipping dislocations with single or double orientations and stacking faults are activated in the alloy. As creep progresses, the amount of slip traces increases to bring about stress concentration and cause microcracks to be initiated and propagated along the grain boundaries up to the rupture of the alloy.