The influence of thermal exposure on the microstructure and stress rupture property of DZ951 nickel-base alloy

The effect of long-term exposure on the microstructure and the stress rupture property of a directionally solidified nickel-base superalloy was investigated. The results show that the MC carbide coarsens and the content of Nb in carbide increases with the rise of aging time. γ′ size increases and γ′ phase rafts with the rise of aging time at different aging temperatures. The driving force of rafting is the decrease of interface energy. There are bimodal γ′ precipitates at the aging temperature of 1100 °C. The stress rupture life at 850 °C/420 MPa reduces with the rise of aging time during aging treatment, which is attributed to the γ′ coarsening and the drop of γ′ volume fraction. The fractographs at different conditions of aging treatments show ductile fracture mode. The fracture surface is related to the morphology and size of γ′ precipitate.