Low Cycle Fatigue And Creep-Fatigue Interaction Behavior Of Nickel Based Superalloy Of GH4169 At Elevated Temperature

A series of tests have been conducted on a nickel based superalloy of GH4169 at elevated temperature of 650 oC,including high temperature oxidation tests,low cycle fatigue tests and creep-fatigue interaction tests.In order to release the superalloy's oxidation behavior,high temperature oxidation tests were to study the micro change of the surface under different exposure times.Applying strain as control parameter,lo w cycle fatigue tests were to know about the superalloy's low cycle fatigue performance.Importing hold period at peak strain,creep-fatigue tests were to study the creep-fatigue interaction behavior of GH4169.Furthermore,the surface and fracture surface of failure samples were observed by scanning electron microscope to analyze the fracture behavior and failure mechanism.The conclusions can be drawn as follows:(1)The oxidation level of GH4169 increases as the increasing high temperature exposure time,manifesting by the oxidation,cracking and flaking of intermetallic compounds.(2)Low cycle fatigue life decreases as the increasing strain amplitude.Besides it shows cyclic softening except for the low strain amplitude of 0.3% and the level of softening increases as the strain amplitude increases.(3)The introduction of hold period decreases fatigue life and before reaching saturation this effect becomes heavier as the elongation of hold period.In addition,the introduction of hold period didn 't change the cyclic softening phenomenon of GH4169.(4)Low cycle fatigue showed brittle fracture,which all initiated from surface of samples.Secondary crack and fatigue striation were the main crack propagation mode.(5)As the increasing of hold period,c rack initiation transformed from single initiation site to multiple sites and the crack propagation changed from transgranular mode to intergranular mode.