Stress dependence of the creep behaviors and mechanisms of a third-generation Ni-based single crystal superalloy

doi:10.1016/j.jmst.2018.11.015

Abstract

Abstract:

Elevated temperature creep behaviors at 1100 °C over a wide stress regime of 120-174 MPa of a third-generation Ni-based single crystal superalloy were studied. With a reduced stress from 174 to 120 MPa, the creep life increased by a factor of 10.5, from 87 h to 907 h, presenting a strong stress dependence. A splitting phenomenon of the close- (about 100 nm) and sparse- (above 120 nm) spaced dislocation networks became more obvious with increasing stress. Simultaneously, a₀<010> superdislocations with low mobilities were frequently observed under a lower stress to pass through γ′ precipitates by a combined slip and climb of two a₀<110> superpartials or pure climb. However, a₀<110> superdislocations with higher mobility were widely found under a higher stress, which directly sheared into γ′ precipitates. Based on the calculated critical resolved shear stresses for various creep mechanisms, the favorable creep mechanism was systematically analyzed. Furthermore, combined with the microstructural evolutions during different creep stages, the dominant creep mechanism changed from the dislocation climbing to Orowan looping and precipitates shearing under a stress regime of 137-174 MPa, while the dislocation climbing mechanism was operative throughout the whole creep stage under a stress of 120 MPa, resulting a superior creep performance.

Key words: Ni-based single crystal superalloy, Creep, Dislocation network, Critical resolved shear stress, Creep mechanism

Quanzhao Yue, Lin Liu, Wenchao Yang, Chuang He, Dejian Sun, Taiwen Huang, Jun Zhang, Hengzhi Fu. Stress dependence of the creep behaviors and mechanisms of a third-generation Ni-based single crystal superalloy[J]. J. Mater. Sci. Technol., 2019, 35(5): 752-763.

Figures/Tables 17

Table 1 Chemical compositions of DD33, Ni bal. (wt%).

Alloy	Cr	Co	Mo	W	Ta	Re	Ti	Al	Hf	C	B
DD33	3.5	9	1.5	6	8	4	0.2	6	0.1	0.02	<0.001

Fig. 1 Diffractometer scans of (004)γ, γ′ peaks of DD33 at (a) room temperature; (b) 1100?°C after holding for 1?h.

Table 2 γ, γ′ lattice parameters and in-situ γ/γ′ lattice misfit at room temperature and at 1100?°C after holding for 1?h measured by high resolution X-ray diffractometer.

	a_γˊ(nm)	a_γI (nm)	a_γII (nm)	δ_γI (%)	δ_γII (%)	δ_av (%)
Heat-treated	0.358452	0.358670	0.358571	-0.061	-0.033	-0.042
1100?°C	0.362678	0.363218	0.363566	-0.245	-0.149	-0.212

Fig. 2 Creep curves at 1100?°C under different stresses. The inset at the top right shows an enlarged partial region of the creep curves in the initial 15 h.

Fig. 3 Strain rate with respect to strain at 1100?°C under a stress of (a) 120?MPa; (b) 137?MPa; (c) 150?MPa; (d) 174?MPa, respectively.

Fig. 4 SEM microstructures of the crept specimen at 1100?°C: (a1) 120?MPa, interrupted in 30?h; (a2) 120?MPa, fractured; (b1) 137?MPa, interrupted in 15?h; (b2) 137?MPa, fractured; (c1) 150?MPa, interrupted in 10?h; (c2) 150?MPa, fractured; (d1) 174?MPa, interrupted in 7?h; (d2) 174?MPa, fractured.

Fig. 5 TEM images showing the dislocation configurations in specimens tested at 1100?°C and 137?MPa after (a) 0.5?h; (b) 15?h; (c) 150?h; (d) fractured state. Beam is close to [001].

Fig. 6 TEM images showing γ/γ′ rafting microstructures in samples tested at 1100?°C and 137?MPa, which were interrupted in (a) 0.5?h; (b) 15?h; (c) 150?h; (d) fractured state after 206?h. Beam is close to [100]. The inset at the bottom left in (d) shows a partial enlargement of the rectangle region with the red borders.

Fig. 7 Schematic diagram showing the relationship between the TEM measurements on (001) plane d(001) and the actual values on (111) plane d(111) of the γ/γ′ interfacial dislocation network spacing: (a) the unit cell of the γ matrix; (b) projection along the (001) plane of (c) one dislocation family with [2ˉ11] line vectors on the (111) interface.

Fig. 8 Analysis results of the distribution of the interfacial dislocation network spacings on {111} planes with all the tests interrupted in the secondary creep stage at 1100?°C and (a) 120?MPa in 30?h; (b) 137?MPa in 15?h; (c) 150?MPa in 10?h; (d) 174?MPa in 7?h.

Fig. 9 (a) Overview bright-field images in the γ′- precipitates of DD33 crept to fracture at 1100?°C under 174?MPa. Burgers vector analysis with dislocations 1-7 under various diffraction conditions. (b) g: 200, (c) g: 220, (d) g: 020, (e) g: 2ˉ20, Beam = [001]; (f) g: 1ˉ31, B = [01ˉ3]; (g) g: 131, (h) g: 3ˉ1ˉ1ˉ, Beam = [1ˉ1ˉ4].

Fig. 10 Weak-beam (g/3?g) dark-field images of the dislocations in Fig. 9 taken with (a, b) g: 200, (c, d) g: 2ˉ20. All images were taken close to the [001] zone axis.

Table 3 Visibility and invisibility of all dislocation segments in Fig. 9.

g		1	2?A	2B	3	4	5	6	7
[001]	200	?	?	?	?	O	?	?	?
	220	?	?	?	?	?	O	O	?
	020	?	?	?	?	?	?	?	?
	2ˉ20	?	?	?	?	?	?	?	?
[01ˉ3	1ˉ31	?	?	O	?	?	?	O	?
[1ˉ1ˉ4	131	?	?	?	O	?	?	?	?
[1ˉ1ˉ4	3ˉ1ˉ1ˉ	?	?	?	O	?	?	?	?

Table 4 Burgers vectors b of all dislocation segments in Fig. 9.

Dislocations	1	2?A	2B	3	4	5	6	7
Burgers vectors b	a₀[100]	a₀[110]	a₀[011ˉ]	a₀[101ˉ]	a₀[11ˉ0]	a₀11ˉ0]	a₀[101ˉ]	a₀[011ˉ]

Fig. 11 Dependence of (a) the secondary creep rate and (b) the quarter root of the secondary creep rate, respectively, on the applied stress at 1100?°C.

Table 5 CRSSs and the corresponding uniaxial stresses for different creep mechanism based on Brown and Ham (B-H) model and Labusch and Schwarz (L-S) model, respectively.

	τOL(MPa)	τPS(MPa)	τDC(MPa)	σOL(MPa)	σPS(MPa)	σDC(MPa)
B-H model	58.8?±?4.8	66.9	10.5?±?0.9	144?±?12	164	25.7?±?2.1
L-S model	79.4?±?6.5	90.4	14.2?±?1.2	195?±?16	222	34.7?±?2.8

Fig. 12 Schematic illustrations of the dominant creep mechanisms during different creep stages in typical creep curves for specimens tested at 1100?°C under stresses of 120?MPa and 137-174?MPa, respectively.

References

[1]	R.C. Reed, The Superalloys: Fundamentals and Applications, CambridgeUniversity Press, Cambridge, 2006.
[2]	B.D. Conduit, N.G. Jones, H.J. Stone, G.J. Conduit, Mater. Des. 131(2017)358-365.
[3]	T.M. Pollock, S. Tin, J. Propuls. Power 22. (2.) (2006) 361-374.
[4]	R.C. Reed, T. Tao, N. Warnken, Acta Mater. 57. (19.) (2009) 5898-5913.
[5]	T.M. Pollock, A.S. Argon, Acta Metall. Mater. 40. (1.) (1992) 1-30.
[6]	M.V. Nathal, L.J. Ebert, Metall. Trans. 16A (3.) (1985) 427-439.
[7]	S.G. Tian, X.J. Zhu, J. Wu, H.C. Yu, D.L. Shu, B.J. Qian, J. Mater. Sci. Technol. 32.(8.) (2016) 790-798.
[8]	L.J. Rowland,USA, 2005.
[9]	T.P. Link, A. Epishin, U. Brückner, P. Portella, Acta Mater. 48. (8.) (2000)1981-1994.
[10]	R.D. Field, T.M. Pollock, W.H. Murphy, et al., in: S.D. Antolovich (Ed.),Superalloys 1992, TMS, Seven Springs, Champion, PA, 1992, pp. 557-566.
[11]	B. Fedelich, A. Epishin, T. Link, H. Klingelh?ffer, G. Künecke, P.D. Portella, et al. PA,2012, pp. 491-500.
[12]	R.C. Reed, N. Matan, D.C. Cox, M.A. Rist, C.M.F. Rae, Acta Mater. 47. (12.) (1999)3367-3381.
[13]	X.P. Tan, J.L. Liu, X.P. Song, T. Jin, X.F. Sun, Z.Q. Hu, J. Mater. Sci. Technol. 27.(10.) (2011) 899-905.
[14]	S. Li, T. Jin, S.G. Tian, Z.Q. Hu, Mater. Sci. Eng. A 454. (2007) 461-466.
[15]	T.P. Gabb, S.L. Draper, D.R. Hull, R.A. Mackay, M.V. Nathal, Mater. Sci. Eng. A118(1989) 59-69.
[16]	G.L. Wang, J.L. Liu, J.D. Liu, T. Jin, X.F. Sun, X.D. Sun, Z.Q. Hu, J. Mater. Sci.Technol. 32. (10.) (2016) 1003-1007.
[17]	J.X. Zhang, T. Murakumo, Y. Koizumi, T. Kobayashi, H. Harada, S. Masaki,Metall. Mater. Trans. A 33. (2002) 3741-3746.
[18]	M.V. Nathal, R.A. MacKay, R.G. Garlick, Scr. Mater. 22. (9.) (1988) 1421-1424.
[19]	H.B. Long, S.C. Mao, S.S. Xiang, Y.H. Chen, H. Wei, Y.Z. Zhou, J.L. Liu, Y.N. Liu,Mater. Des. 126(2017) 12-17.
[20]	N. Miura, Y. Kondo, N. Ohi, et al., in: T.M. Pollock (Ed.), Superalloys 2000, TMS,Seven Springs, Champion, PA, 2000, pp. 377-385.
[21]	M. Feller-Kniepmeier, T. Link, Mater. Sci. Eng. A 113. (1989) 191-195.
[22]	T.M. Pollock, R.D. Field, Dislocation and high-temperature plastic deformationof superalloy single crystal, in: F.R.N. Nabarro, M.S. Duesbery (Eds.),Dislocations in Solids, vol. 11, Elsevier, Amsterdam, 2002, pp. 593-595.
[23]	C. Fu, Y.D. Chen, X.F. Yuan, S. Tin, S. Antonov, K. Yagi, Q. Feng, J. Mater. Sci.Technol. 35(2019) 223-230.
[24]	J.X. Zhang, T. Murakumo, H. Harada, Y. Koizumi, Scr. Mater. 48. (3.) (2003)287-293.
[25]	X.G. Wang, J.L. Liu, T. Jin, X.F. Sun, Y.Z. Zhou, Z.Q. Hu, J.H. Do, B.G. Choi, I.S. Kim,C.Y. Jo, Mater. Sci. Eng. A 626. (2015) 406-414.
[26]	T.P. Link, A. Epishin, M. Klaus, U. Brückner, A. Reznicek, Mater. Sci. Eng. A 405.(2005) 254-265.
[27]	C. Yuan, J.T. Guo, H.C. Yang, S.H. Wang, Scr. Mater. 39. (7.) (1998) 991-997.
[28]	S. Tang, L.K. Ning, T.Z. Xin, Z. Zheng, J. Mater. Sci. Technol. 32. (2.) (2016)172-176.
[29]	S.G. Tian, Y. Su, B.J. Qian, X.F. Yu, F.S. Liang, A.A. Li, Mater. Des. 37(2012)236-242.
[30]	B. Reppich, Acta Metall. 30(1982) 87-94.
[31]	G. Bruno, G. Schumacher, H.C. Pinto, C. Schulze, Metall. Mater. Trans. A 34. (2.)(2003) 193-197.
[32]	A. Royer, P. Bastie, D. Bellet, J.L. Strudel, Philos. Mag. A 72. (3.) (1995) 669-689.
[33]	G. Schumacher, N. Darowski, I. Zizak, H. Klingelh?ffer, W. Chen, W. Neumann,Trans. Tech. Publ. 539(2007) 3048-3052.
[34]	Y.L. Tang, M. Huang, J.C. Xiong, J.R. Li, J. Zhu, Acta Mater. 126(2016) 336-345.
[35]	A.J.E..Foreman, Acta Metall. 3(1955) 322-330.
[36]	D.C. Chrzan, M.J Mills, in: F.R.N. Nabarro, M.S. Duesbery (Eds.), Dislocations inSolids, Volume 10: L12Ordered Alloys, Elsevier, Amsterdam, 1996, pp.187-252.
[37]	L.J. Carroll, Q. Feng, T.M. Pollock, Metall. Mater. Trans. A 39. (2008) 1290-1307.
[38]	L. Dirand, J. Cormier, A. Jacques, J.P. Chateau-Cornu, T. Schenk, O. Ferry, P. Bastie, Mater. Charact. 77(2013) 32-46.
[39]	M. Véron, P. Bastie, Acta Mater. 45. (8.) (1997) 3277-3282.
[40]	J.X. Zhang, T. Murakumo, Y. Koizumi, H. Harada, J. Mater. Sci. 38. (24.) (2003)4883-4888.
[41]	Q.Z. Yue, L. Liu, W.C. Yang, T.W. Huang, J. Zhang, H.Z. Fu, Mater. Sci. Eng. A 742.(2019) 132-137.
[42]	J.X. Zhang, T. Murakumo, Y. Koizumi, T. Kobayashi, H. Harada, Acta Mater. 51(2003) 5073-5081.
[43]	G. Eggeler, A. Dlouhy, Acta Mater. 45(1997) 4251-4262.
[44]	F.R.N. London,H.L. de Villiers, The Physics of Creep, Taylor & Francis, London,1995.
[45]	L.M. Brown, P.K. Ham, in: A. Kelly, R.B. Nicholson (Eds.), StrengtheningMethods in Crystals, Elsevier, Amsterdam, 1971.
[46]	R.S.W. Shewfelt, L.M. Brown, Philos. Mag. 35. (4.) (1977) 945-962.
[47]	L.Q. Cui, J.J. Yu, J.L. Liu, T. Jin, X.F. Sun, Mater. Sci. Eng. A 710. (2018) 309-317.
[48]	E.A. Marquis, D.C. Dunand, Scr. Mater. 47(2002) 503-508.
[49]	B. Reppich, P. Schepp, G. Wehner, Acta Metall. 30(1982) 95-104.