Effect of Aging Heat Treatment on the Microstructure and Creep Properties of the Cast Ni-Based Superalloy at Low Temperature

Effect of aging heat treatment on the grain boundary microstructure and creep properties of a cast Ni-based superalloy was investigated. With increasing aging temperature from 750 to 1000 °C, M 23 C 6 carbides along the grain boundaries evolve from fine distributed block, continuous film into the coarse discrete block. Moreover, the M 23 C 6 carbides are mainly enveloped within γ ′ layers along grain boundaries during 1000 °C aging. Creep rupture lifetime and elongation at 760 °C and 645 MPa are improved with increasing the aging temperature. In particular, the creep rupture lifetime of the specimens aging at 1000 °C is one order of magnitude higher than that of the specimens aging at 750 °C. The enhancement of ductility induced by the γ ′ envelopes plays a significant role in the improvement of creep rupture lifetime.