High Temperature Fatigue Behavior of Powder Metallurgy FGH4720Li Nickel-Based Superalloy

Powder metallurgy FGH4720Li Nickel-based superalloy samples were token from a turbine disk web plate, mortise groove and disk center. High temperature low cycle fatigue tests were conducted on the samples at temperature of 500 ℃, maximum stress of 1180 MPa and stress ratio of 0.05. The high temperature fatigue behavior was studied, and the fatigue fracture mechanism and the effect of inclusions characteristics on fatigue life were analyzed. The results show that under the action of high temperature cyclic stress, the average fatigue life of the web plate, mortise groove and disk center sample was 280 413, 226 706, 177 406 cycle, respectively, and the fatigue life variable coefficient was 0.47, 0.57, 0.51, respectively. The high temperature fatigue fracture mechanism of the turbine disk included slip-induced pseudo-bifurcation fracture and the initial fracture of alumina inclusions. The high temperature fatigue life N was influenced by the crack source area equivalent radius r, the inclusion projected area S and the inclusion minimum distance d from the sample surface. The fitting relationship was obtained as follows: N=113857×lg（rd/S）+7880.