Research On Fracture Properties And Fatigue Properties Of Superalloys Gh4169 Welded Joints

As the heart of the aeroplane, fatigue properties of welded joints of air craft engine material related to the development of the entire aviation industry , this paper studied the fracture properties and fatigue properties of welded joints of superalloy GH4169 which is widely used in the air craft engine.To finish the engineering critical assessment for the welded joints of superalloy GH4169, we obtain the fracture toughness of the weld and the heat affected zone by peforming the CTOD experiments which based on the regulations and the principles of the BS7448 standard at room temperature. The results show that the fracture toughness of the weld metal and the HAZ are far less than this property of body metal, the average CTOD value of the weld metal and the HAZ are 0.03837 mm and 0.04153 mm, which are about 35% of that of the body metal.Study on the crack growth rate of GH4169 superalloy used in aero-engine. The results show the parameters in the Paris law at 50% survival rate; The results show that the superalloy (GH4169) weld joints of the Paris fatigue crack growth rate expression parameters m = 3.64, C = 3.45E-10 (50% survival rate); base metal of the Paris fatigue crack growth rate expression parameter m = 3.56, C = 8.085E-10 (50% survival rate), indicating that the GH4169 alloy after high-temperature electron-beam welding seam of crack growth rate lower than the parent material of the crack growth rate,which means the weld joints of the superalloy GH4169 have better properties of crack arresting than that properties of base metal.According the parameters of the mechanics property and fracture toughness, we perform the relevant assessment in the standard BS7910 to determine the critical/tolerable size of surface cracks at weld toes about T welded joints; after that, according the crack growth rate and a known flaw, we estimate the rest Cycle life when the known crack propagating to the maximum tolerable size based on the standard BS7910.Experiment on TIG welded joints of superalloy GH4169 have been performed in order to research the behavior under low cycle condition. We obtain the low cycle parameters of the welded joints at room temperature by the experiment; then figure out the curves about the stress-strain and the strain-cycle life. The experiment results reveal that the low cycle behavior of the superalloy(GH4169) welded joints according with the Coffin-Manson expressions.