Effect of Skew Angle of Holes on the Thermal Fatigue Behavior of a Ni-based Single Crystal Superalloy

doi:10.1007/s40195-016-0514-y

Abstract

Abstract:

In the present work, holes of various skew angles were electrochemically machined in the middle of the plate specimens in a Ni-based single crystal superalloy and crack initiation and propagation around holes during thermal fatigue cycles (20-1100 °C) were investigated. It was demonstrated that the skew angles had a significant effect on the initiation and propagation of thermal fatigue cracks. During thermal fatigue process, stress concentration occurred at the edge of the holes. As for skew angles, the maximum stress concentration appeared at the acute side of holes. The maximum stress concentration resulted in plastic deformation at the acute side of the 30° hole, driving the thermal fatigue cracks to initiate after 220 cycles and propagate along \([0\bar{1}1]\) direction. However, the stresses concentrated at the edge of 90° or 60° holes were not large enough to initiate cracks even after 580 thermal cycles. This work will help to understand the local deformation behavior in the vicinity of cooling holes with various skew angles and have serious design implications for turbine blades.

Key words: Ni-based single crystal superalloy, Thermal fatigue properties, Holes, Skew angles, Cracks

Zhong-Jiao Zhou,Da-Qian Yu,Li Wang,Lang-Hong Lou. Effect of Skew Angle of Holes on the Thermal Fatigue Behavior of a Ni-based Single Crystal Superalloy[J]. Acta Metallurgica Sinica (English Letters), 2017, 30(2): 185-192.

Figures/Tables 8

Fig. 1 a Dendritic structure of the experimental alloy, b two-phase γ/γ′ microstructure of specimens after heat treatment

Fig. 2 Schematic of Ni-based SX superalloy samples for TF tests a, schematic illustration of skew holes b, the obtuse and acute sides on the cross section c

Fig. 3 Morphologies of holes of different skew angles: aα = 90°, bα = 60°, cα = 30°

Fig. 4 Crack growth kinetics of samples with different skew angles

Fig. 5 Microstructure around the hole (20 cycles)

Fig. 6 Initiation and propagation of cracks around 30° holes: a, b 120 cycles, c, d 180 cycles, e 260 cycles, f 540 cycles, g, h zoomed view of marked area in f

Fig. 7 Microstructural evolution around 60° holes during TF tests: a 100 cycle, b zoomed view of rectangular area in a, c 180 cycles, d 540 cycles

Fig. 8 Changes in 90° holes after TF: a 140 cycles, b zoomed view of rectangular area in a, c 540 cycles, d zoomed view of rectangular area in c

References

[1]	A.E. Gemma, J.S. Phillips, Eng. Fract. Mech. 9, 25(1977)
[2]	F. Sun, J.Y. Tong, Q. Feng, J.X. Zhang, J. Alloys Compd. 618, 728(2015)
[3]	F.M. Olbersleben, N. Kasik, B. Ilschner, F. Réza?-Aria, Metall. Mater. Trans. A 30, 981 (1999)
[4]	V.S. Bhattachar, Int. J. Fatigue 17, 407 (1995)
[5]	P.A. Sabnis, M. Maziere, S. Forest, N.K. Arakere, F. Ebrahimi, Int. J. Plast 28, 102 (2012)
[6]	C.L. Dong, X.G. Yang, D.Q. Shi, H.C. Yu, Mater. Des. 55, 966(2014)
[7]	J.W.H. Price, B. Kerezsi, M. Chang, Eng. Fail. Anal. 11, 267(2004)
[8]	E. Glenny, T.A. Taylor, J. Inst. Metal. 88, 449(1959)
[9]	D.A. Woodford, D.F. Mowbray, Mater. Sci. Eng. A 16, 5 (1974)
[10]	P.C. Xia, J.J. Yu, X.F. Sun, H.R. Guan, Z.Q. Hu, Rare Metal Mater. Eng. 37, 50(2008)
[11]	Y. Liu, J.J. Yu, Y. Xu, X.F. Sun, Rare Metal Mater. Eng. 38, 59(2009)
[12]	L. Wang, Z.J. Zhou, W.G. Jiang, D. Wang, J. Shen, L.H. Lou, Chin. J. Mater. Res. 28, 663(2014)
[13]	L. Wang, Z.J. Zhou, S.H. Zhang, X.D. Jiang, L.H. Lou, J. Zhang, Acta Metall. Sin. 51, 1273(2015). (in Chinese)
[14]	B. Baufeld, E. Tzimas, H. Müllejans, S. Peteves, J. Bressers, W. Stamm, Mater. Sci. Eng. A 315, 231 (2001)
[15]	Z.X. Jin, J. Iron. Steel Res. Int. 5, 205(1985)
[16]	Y. Zhou, S.X. Rao, Z. Zhang, Z.H. Zhao, Mater. Des. 49, 25(2013)
[17]	X.M. Wang, Y. Zhou, Z.H. Zhao, Z. Zhang, Acta Metall. Sin. (Engl. Lett.) 28, 628(2015)
[18]	S. Nagpal, N. Jain, S. Sanyal, Eng. J. 16, 1(2012)
[19]	F. Ellyin, Exp. Mech. 13, 305(1973)
[20]	Z.J. Zhou, L. Wang, J.L. Wen, L.H. Lou, J. Zhang, J. Alloys Compd. 628, 158(2015)
[21]	E. Sun, T. Heffernan, R. Helmink, Superalloys 2012, 351(2012)
[22]	C.L. Brundidge, D. Vandrasek, B. Wang, T.M. Pollock, Metall. Mater. Trans. A 43, 965 (2012)
[23]	Z.D. Fan, D. Wang, L.H. Lou, Acta Metall. Sin. (Engl. Lett.) 28, 152(2015)
[24]	T. Ichitsubo, D. Koumoto, M. Hirao, K. Tanaka, M. Osawa, T. Yokokawa, H. Harada, Acta Mater. 51, 4033(2003)
[25]	N. Matan, D.C. Cox, C.M.F. Rae, R.C. Reed, Acta Mater. 47, 2031 (1999)