Detection and analysis of high temperature fatigue fracture surface oxygen diffusion of GH4133B superalloy used in turbine disk of aero-engine

The chemical contents on the fatigue fracture surface of GH4133B superalloy piece suffering tension-tension fatigue and operated at high temperature 600 oC is analyzed using an energy dispersive spectrometer, and the element content percentages at the position of carbide inclusion and that of second-phase particle in the fatigue source region are measured. It is shown that under the conditions of high temperature and air environment, the carbon element in the carbide inclusion can be easily oxidized, which results in accelerating fatigue crack nucleation and microcrack generation, reducing the fatigue crack initiation lifetime. The oxygen concentration is detected on the fatigue fracture surface along the crack propagation direction, the oxygen diffusion model is constructed, and the oxygen concentration gradient equation is derived. It is found that the oxygen content decreases gradually along the crack propagation direction, suggesting that at the crack initiation and short crack propagation stage, the alloy element reacts sufficiently with oxygen for a long time, and the oxidation accelerates the crack initiation, while at the long crack growth stage, the crack propagation rate is faster, so the alloying elements do not have adequate time for reacting with oxygen, resulting in the low oxygen content, and the oxidation has a small influence on the long crack propagation rate.