Research on Transition from Short to Long Fatigue Crack Propagation of GH4133B Superalloy Used in Turbine Disk of Aero-Engine

Abstract:

The fatigue crack propagation tests for circular notched compact tension specimens of GH4133B superalloy used in a turbine disk of aero-engine are carried out at room temperature. The test data shows that in the transition region from short to long crack growth, the crack growth rate appears as a fluctuation form with acceleration following deceleration. A quasi harmonic function is constructed to model the fatigue crack growth in the transition region, and the result indicates that such function is suitable to describe the crack growth behavior. A metallographic analysis with respect to microscopic observation for the specimen’s surface suggests that the wave period, that is, a step length of a cycle fluctuation from acceleration to deceleration on the crack growth rate curve is agree well with the intrinsic scale of grain size, which indicates that in the transition region from short to long crack growth, grain boundary plays a dominant role in crack growth rate. Finally, the fracture surfaces of specimen are observed using a scanning electron microscopy. It can be found from the fracture surface morphologies that in the transition region from short to long crack growth, the stress intensity factor range is still lower than the fatigue crack growth threshold ΔK_th, the effect of microstructure, such as grain size, grain boundary, secondary phase particle, and inclusion ahead of the crack tip, and the effect of crack closure on crack growth behavior should be considered, the local further plastic deformation at crack tip will meet larger resistance, so some twin bands are observed on the fracture surface. As crack length increases with increasing fatigue cycle, the crack propagation is noted to change from a transgranular crack propagation mode, a mixed transgranular and intergranular crack propagation nature, to intergranular crack propagation manner.

• Periodical: Key Engineering Materials (Volume 697)
• Pages: 664-669
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.697.664
• Online since: July 2016
• Authors: Rong Guo Zhao*, Qi Bang Li, Yong Zhou Jiang, Xi Yan Luo, Ya Feng Liu, Yi Yan, Peng Cai, Yue Chen
• Keywords: Fatigue, Fatigue Crack Growth Rate, GH4133B Superalloy, Long Crack, Short Crack

References

[1] R.G. Zhao, X.Y. Luo, L.L. Ren, H.C. Li, X.J. Li, X.H. Liu. Research on fatigue crack propagation behavior of GH4133B superalloy used in turbine disk of aero-engine. Journal of Mechanical Engineering, 47(18) (2011): 55-66. (in Chinese).

DOI: 10.3901/jme.2011.18.055

[2] R.G. Zhao, W. Li, Y.Z. Jiang, X.Y. Luo, J.F. Li, Q.B. Li, Y.F. Liu, Y. Yan. Fatigue short crack growth and mechanism of GH4133B superalloy used in turbine disk of aero-engine. Key Engineering Materials, 602-603 (2014): 671-676.

DOI: 10.4028/www.scientific.net/kem.602-603.671

[3] C.A. Rodopoulos, E.R. de los Rios. Theoretical analysis on the behaviour of short fatigue cracks. International Journal of Fatigue, 24(7) (2002): 719-724.

DOI: 10.1016/s0142-1123(01)00196-7

[4] U. Krupp, O. Düber, H. -J. Christ, B. Künkler, P. Köster, C. -P. Fritzen. Propagation mechanisms of microstructurally short cracks – Factors governing the transition from short- to long-crack behavior. Materials Science and Engineering A, 462(1-2) (2007).

DOI: 10.1016/j.msea.2006.03.159

[5] B. Künkler, O. Düber, P. Köster, U. Krupp, C. -P. Fritzen, H. -J. Christ. Modelling of short crack propagation – Transition from stage I to stage II. Engineering Fracture Mechanics, 75(3-4) (2008): 715-725.

DOI: 10.1016/j.engfracmech.2007.02.018

[6] W. Elber. Fatigue crack closure under cyclic tension. Engineering Fracture Mechanics, 2(1) (1970): 37-45.

DOI: 10.1016/0013-7944(70)90028-7