Thermal cycling creep properties of a directionally solidified superalloy DZ125

doi:10.1016/j.jmst.2021.07.015

Abstract

Abstract:

Aero-engine turbine blades may suffer overheating during service, which can result in severe microstructural and mechanical degradation within tens of seconds. In this study, the thermal cycling creep under (950℃/15 min+1100℃/1 min)-100 MPa was performed on a directionally solidified superalloy, DZ125. The effects of overheating and thermal cycling on the creep properties were evaluated in terms of creep behavior and microstructural evolution against isothermally crept specimens under 950℃/100 MPa, 950℃/270 MPa, and 1100℃/100 MPa. The results indicated that the thermal cycling creep life was reduced dramatically compared to the isothermal creep under 950℃/100 MPa. The plastic creep deformation mainly occurred during the overheating stage during the thermal cycling creep. The thermal cycling creep curve exhibited three stages, similar to the 1100℃ isothermal creep, but its minimum creep rate occurred at a lower creep strain. The overheating events caused severe microstructural degradation, such as substantial dissolution of γ' phase, earlier formation of rafted γ' microstructure, widening of the γ channels, and instability of the interfacial dislocation networks. This microstructural degradation was the main reason for the dramatic decrease in thermal cycling creep life, as the thermal cycling promoted more dislocations to cut into γ' phase and more cracks to initiate at grain boundaries, carbides, and residual eutectic pools. This study underlines the importance of evaluating the thermal cycling creep properties of superalloys to be used as turbine blades and provides insights into the effect of thermal cycling on directionally solidified superalloys for component design.

Key words: Directional solidified superalloy, Thermal cycling creep, Overheating, Creep properties, Microstructural degradation

Wenrui An, Satoshi Utada, Xiaotong Guo, Stoichko Antonov, Weiwei Zheng, Jonathan Cormier, Qiang Feng. Thermal cycling creep properties of a directionally solidified superalloy DZ125[J]. J. Mater. Sci. Technol., 2022, 104: 269-284.

Figures/Tables 16

Table 1 Measured chemical composition of DZ125 superalloy (wt.%).

Ni	Co	Cr	W	Al	Mo	Ta	Hf	Ti	C	B
Bal.	10.0	8.9	7.0	5.2	2.0	3.8	1.5	0.9	0.1	0.015

Fig. 1. Schematic of the thermal cycling creep testing history and the interrupted testing points (1#, 2#, 3#, and 1’#).

Table 2 Specimen names for different test conditions of DZ125 superalloy.

Test type	Specimen names	Test conditions
Thermal exposure	TS₉₅₀	Thermal exposure at 950℃/6 h
	TE₉₅₀ [26]	Thermal exposure at 950℃/900 h
	TE₁₀₅₀ [26]	Thermal exposure at 1050℃/900 h
	TE₁₁₀₀ [26]	Thermal exposure at 1100℃/900 h
Isothermal creep	I₉₅₀-IR	Interrupted after 950℃/98 MPa for 100 h with <0.1% strain
	I₉₅₀-NF*	Creep under 950℃/100 MPa*
	I₉₅₀-F	Failure under 950℃/270 MPa with 19% strain
	I₁₁₀₀-IR	Interrupted at 1% strain under 1100℃/100 MPa
	I₁₁₀₀-F	Failure under 1100℃/100 MPa with 33% strain
Thermal cycling creep	N_0.5-2#	Interrupted at the end of 1100℃ stage with 0.5% plastic creep strain
	N_1.0-1#	Interrupted at 15^th min of 950℃ stage with 1% plastic creep strain
	N_1.0-2#	Interrupted at the end of 1100℃ stage with 1% plastic creep strain
	N_1.0-3#	Interrupted at 1^st min of of 950℃ stage with 1% plastic creep strain
	N_F	Failure after 0.5 min at 1100℃ during the 321^st cycle with 29% placstic strain

Fig. 2. Creep curves of DZ125 superalloy under the thermal cycling creep and different isothermal creep conditions. (a) Raw experimental strain vs. time curve during thermal cycling creep (NF specimen); (b) plastic creep strain vs. time curve and (c) plastic creep rate vs. strain curve during isothermal creep under 950℃/270 MPa (I950-F specimen) and 1100℃/100 MPa (I1100-F specimen), and thermal cycling creep (NF specimen). The temperature profile and the associated raw experimental strain change during the (d) 105th, (e) 292th and (f) 320th cylce of thermal cycling creep. (g) Measurement of plastic strain increment at different stages of the thermal cycle during the thermal cycling creep.

Table 3 Creep life, minimum creep rate and duration at 1100℃ of the isothermal creep under 950℃/100 MPa, 950℃/270 MPa and 1100℃/100 MPa, as well as the thermal cycling creep under (950 ℃/15 min-1100 ℃/1 min)/100 MPa of DZ125 superalloy.

Specimen name	Rupture life (h)	Minimum creep rate (10^-8 s^-1)	Strain corresponds to the minimum creep rate (%)	Duration at 1100℃ (h)	Number of grains**
I₉₅₀-NF*	>10⁵ *	N/A	N/A	0	N/A
I₉₅₀-F	105.4	4.5	0.38	0	10
I₁₁₀₀-F	19.0	19.2	0.59	19.0	17
N_F	96.2	11.8	0.36	5.4	16

Fig. 3. Typical microstructure of as-received DZ125 superalloy. (a) OM image of columnar grains along the longitudinal section. SEM images of (b) the carbides and γ/γ’ eutectic pools in the interdendritic region, (c) γ’ precipitates in the dendrite core area along the cross section. SEM images of grain boundary with (d) carbides chain and (e) M6C film.

Fig. 4. Typical microstructure of I950-IR (isothermal creep under 950℃/98 MPa for 100h) specimen. SEM images of γ’ precipitates in the dendrite cores along the (a) cross section and (b) longitudinal section; (c) TEM images of dislocation configurations in the dendrite region; SEM images of (d) interdendritic carbides, (e) a grain boundary with MC, M6C and M23C6 carbides.

Fig. 5. Typical microstructure of I1100-IR (isothermal creep under 1100℃/100 MPa with 1% strain) specimen. SEM images of γ′ precipitates in the dendrite cores along the (a) cross section and (b) longitudinal section; (c) TEM images of dislocation configurations in the dendrite region. SEM images of (d) interdendritic carbides and (b) a carbide-free grain boundary and (f) the cracked surface carbides.

Table 4 Number of grains, creep time, γ′ volume fraction, γ channel width, γ′ thickness and average dislocation network spacings of DZ125 superalloy under different creep conditions and thermal exposure conditions.

Test type	Specimen name	No. of grains	Strain (%)	Time (h)	Cycles	γ' volume fraction (%)	γ channel width (nm)	γ′ thickness (nm)	Average dislocation network spacing (nm)
Thermal exposure	TE₉₅₀ [26]	N/A	N/A	900	N/A	63.7±3.2	N/A	N/A	N/A
	TE₁₀₅₀ [26]	N/A	N/A	900	N/A	49.3±3.3	N/A	N/A	N/A
	TE₁₁₀₀ [26]	N/A	N/A	900	N/A	39.5±4.3	N/A	N/A	N/A
Interrupted isothermal creep	I₉₅₀-IR	N/A	<0.1	100	N/A	65.7±2.8	N/A	N/A	N/A*
	I₁₁₀₀-IR	11	1	5.2	N/A	47.7±3.6	431±29	310±18	75±14
Interrupted thermal cycling creep	N_1.0-1#	17	1	10.8	36	49.0±3.8	427±27	315±31	90±9
	N_1.0-2#	8	1	23.7	78	46.0±4.0	480±10	297±20	98±12
	N_1.0-3#	7	1	20.1	66	45.1±2.9	444±30	319±35	96±10

Fig. 6. Typical microstructure of I1100-F (isothermal creep to failure under 1100℃/100 MPa) specimen. OM image of morphology (a) along the longitudinal section of fracture surfaces, as well as higher magnification images of morphology near the surface along the longitudinal section (b) 7.5 mm, (c) 6.5 mm and (d) 5.6 mm from the fracture. SEM images of (b) surface cracks, (c) grain boundary cracks and (d) grain interior cracks.

Table 5 The density of surface cracks and internal cracks of I1100-F and NF specimens.

Specimen		I₁₁₀₀-F	N_F
Surface cracks	Count per length (#/mm)	14.8	35.3
Internal cracks*	Count per area (#/mm^-2)	9.9	43.8

Fig. 7. SEM images of γ’ precipitates in the dendrite cores of DZ125 superalloy after the interrupted thermal cycling creep with 1% plastic creep strain: (a)N1.0-1#, (b)N1.0-2# and (c)N1.0-3#; along the (1) cross section and (2) longitudinal section.

Fig. 8. TEM images of dislocation configurations in the dendrite region of different interrupted plastic creep strain during the thermal cycling creep: (a) N0.5-2#, (b) N1.0-1# and (c) N1.0-2#, B = [001].

Fig. 9. Typical microstructure in the interdendritic region and surface of DZ125 superalloy after interrupted thermal cycling creep specimens with 1% plastic creep strain. SEM images of (a) carbides in N1.0-1#, (b) fractured surface oxidized carbides in N1.0-1# and (c) carbides-free grain boundary in N1.0-2#.

Fig. 10. Typical microstructure of NF (thermal cycling creep to failure) specimen. OM images of morphology (a) along longitudinal section of fracture surfaces, as well as higher magnification images of near the surface along the longitudinal section (b) 7.5 mm, (c) 6.5 mm and (d) 5.6 mm from the fracture. SEM images of (e) surface cracks, (f) a higher magnification corresponding to the contents in the box in (e), (g) fractured surface carbide, (h) grain boundary cracks and (i) grain interior cracks.

Fig. 11. SEM images of carbides of TS950 (thermal exposure at 950℃ for 6 h) specimen: fractured carbides (a) in surface observed on top view and (b) near surface observed along cross section, (c) unfractured internal carbides observed along cross section.

References 61

[1]	W.X. Zhao, Y. Li, Y.W. Fan, Y.R. Zheng, J. Mater. Eng. Perform. 8 (2012) 39, doi: 10.3969/j.issn.1001-4381.2013.06.001. DOI
[2]	J. Cormier, X. Milhet, J.L. Champion, J. Mendez, Adv. Eng. Mater. 10 (1-2) (2008) 56-61, doi: 10.1002/adem.200700248. DOI URL
[3]	H.M. Tawancy, L.M. Al-Hadhrami, Eng. Fail. Anal. 16 (1) (2009) 273-280, doi: 10.1016/j.engfailanal.2008.05.001. DOI URL
[4]	X.T. Guo, W.W. Zheng, C.B. Xiao, L.F. Li, S. Antonov, Y.R. Zheng, Q. Feng, Eng. Fail. Anal. 103 (2019) 308-318, doi: 10.1016/j.engfailanal.2019.04.021. DOI URL
[5]	J. Cormier, in: M. Hardy, E. Huron, U. Glatzel, B. Griffin, B. Lewis, C. Rae, V.t Seetharaman, S. Tin (Eds.), Superalloys 2016: Proceedings of the 13th Inte-national Symposium of Superalloys, John Wiley & Sons, Inc. Hoboken, NJ, USA, 2016, pp. 383-394.
[6]	C.L. Corey, J.P. Rowe, J.W. Freeman, Progress report to the National Advisory Committee for Aeronautics covering research on heat-resistant alloys, Michi-gan, University of Michigan, Michigan, 1955.
[7]	J.P. Rowe, J.W. Freeman, Effect of overheating on the creep-rupture properties of HS31 alloy, University of Michigan, Michigan, 1956.
[8]	J.P. Rowe, J.W. Freeman, H.R. Voorhees, Final report to the General Electric Company Aircraft Gas Turbine Division on Effect of Overheating on the Creep- -Rupture Properties of Udimet500 alloy at 16000 °F and 28,50 0 PSI, University of Michigan, Michigan, 1957.
[9]	J.P. Rowe, J.W. Freeman, Final report to National Aeronautics and Space Ad-ministration: Effect of overheating on crept-rupture properties of M252 and Inconel700 alloys at 1500 and 1600, University of Michigan, Michigan, 1960.
[10]	J.P. Rowe, J.W. Freeman, Final report to National Aeronautics and Space Ad-ministration: Relations between microstructure and creep-rupture properties of Nickel-base alloys as revealed by overtemperature exposures, University of Michigan, Michigan, 1961.
[11]	J. Cormier, X. Milhet, J. Mendez, Acta Mater. 55 (18) (2007) 6250-6259, doi: 10.1016/j.actamat.2007.07.048. DOI URL
[12]	J. Cormier, M. Jouiad, F. Hamon, P. Villechaise, X. Milhet, Phil. Mag. Lett. 90 (8) (2010) 611-620, doi: 10.1080/09500839.2010.489887. DOI URL
[13]	R. Giraud, J. Cormier, Z. Hervier, D. Bertheau, K. Harris, J. Wahl, X. Mil-het, J. Mendez, A. Organista, in: E.S. Huron, R.C. Reed, M.C. Hard, M.J. Mills, R.E. Montero, P.D. Portella, J. Telesman (Eds.), Superalloys 2012: Proceedings of the 12th International Symposium on Superalloys, John Wiley & Sons, Inc. Hoboken, NJ, USA, 2012, pp. 265-274.
[14]	C. Schwalbe, J. Cormier, C. Jones, E. Galindo-Nava, C. Rae, Metall. Mater. Trans. A 49 (9) (2018) 3988-4002, doi: 10.1007/s11661-018-4764-3. DOI URL
[15]	B. Viguier, F. Touratier, E. Andrieu, Philos. Mag. 91 (35) (2011) 4427-4446, doi: 10.1080/14786435.2011.609151. DOI URL
[16]	A. Raffaitin, D. Monceau, F. Crabos, E. Andrieu, Scr. Mater. 56 (4) (2007) 277-280, doi: 10.1016/j.scriptamat.2006.10.026. DOI URL
[17]	X. Guo, W. Zheng, W. An, S. Antonov, L. Li, J. Cormier, Q. Feng, Materialia 14 (2020) 100913, doi: 10.1016/j.mtla.2020.100913. DOI URL
[18]	X.F. Yuan, W.R. An, Y.W. Ju, S. Antonov, Z.N. Bi, W. Li, J.T. Wu, Mater. Charact. 158 (2019) 109946, doi: 10.1016/j.matchar.2019.109946. DOI URL
[19]	S. Antonov, W.R. An, S. Utada, X.T. Guo, C. Schwalbe, W.W. Zheng, C.M.F. Rae, J. Cormier, Q. Feng, in: S. Tin, M. Hardy, J. Clews, J. Cormier, Q. Feng, J. Marcin, C. O’Brien, A. Suziki (Eds.), Superalloys 2020: Proceedings of the 14th Intenational Symposium of Superalloys Springer International, Springer International Publishing, Cham, Switzerland, 2020, pp. 228-239, doi: 10.1007/978-3-030-51834-9_22. DOI
[20]	R.C. Reed, The Superalloys: Fundamentals and Applications, Cambridge Univer-sity Press, London, 2006.
[21]	F.I. Versnyder, M.E. Shank, Mater. Sci. Eng. 6 (4) (1970) 213-247, doi: 10.1016/0025-5416(70)90050-9. DOI URL
[22]	L.M. Suave, J. Cormier, P. Villechaise, D. Bertheau, G. Benoit, F. Mauget, G. Cail-letaud, L. Marcin, in: M. Hardy, E. Huron, U. Glatzel, B. Griffin, B. Lewis, C. Rae, V.t Seetharaman, S. Tin (Eds.), Superalloys 2016: Proceedings of the 13th Inte-national Symposium of Superalloys, John Wiley & Sons, Inc. Hoboken, NJ, USA, 2016, pp. 745-756.
[23]	S.G. Tian, N. Tian, H.C. Yu, X.L. Meng, Y. Li, Mater. Sci. Eng. A 615 (2014) 469-480, doi: 10.1016/j.msea.2014.07.103. DOI URL
[24]	L.Z. He, Q. Zheng, X.F. Sun, H.R. Guan, Z.Q. Hu, A.K. Tieu, C. Lu, H.T. Zhu, Mater. Sci. Eng. A 397 (1-2) (2005) 297-304, doi: 10.1016/j.msea.2005.02.038. DOI URL
[25]	Y.L. Cai, Y.R. Zheng, Metallographic Research of Superalloys, National Defense Industry Press, Beijing, 1986.
[26]	Y.D. Chen, W.W. Zheng, Y.R. Zheng, Q. Feng, J. Chin., Rare Metals 42 (10) (2018) 10.13373/j.cnki.cjrm.xy17090026. DOI
[27]	Y.D. Chen, Assessment of Normal Service-Induced Damage in High Pressure Turbine Blades Made of Directionally-Solidified Superalloy DZ125, University of Science and Technology of Beijing, Beijing, 2017.
[28]	F. Torster, G. Baumeister, J. Albrecht, G. Lütjering, D. Helm, M.A. Daeubler, Mater. Sci. Eng. A 234-236 (1997) 189-192, doi: 10.1016/S0921-5093(97)00161-5. DOI URL
[29]	X. Yan, K. Zhang, Y. Deng, R. Sun, L. Lin, X. Zhang, Propuls. Power Res. 3 (3) (2014) 143-150, doi: 10.1016/j.jppr.2014.07.004. DOI URL
[30]	J. Cormier, X. Milhet, F. Vogel, J. Mendez, in: R.C. Reed, K.A. Green, P. Caron, T.P. Gabb, M.G. Fahrmann, E.S. Huron (Eds.), Superalloys 2008: Proceedings of the 11th Intenational Symposium of Superalloys, John Wiley & Sons, Inc. Hobo-ken, NJ, USA, 2008, pp. 941-949.
[31]	J.B. le Graverend, L. Dirand, A. Jacques, J. Cormier, O. Ferry, T. Schenk, F. Gallerneau, S. Kruch, J. Mendez, Metall. Mater. Trans. A 43 (11) (2012) 3946-3951, doi: 10.1007/s11661-012-1343-x. DOI URL
[32]	J.B. le Graverend, A. Jacques, J. Cormier, O. Ferry, T. Schenk, J. Mendez, Acta. Mater. 84 (0) (2015) 65-79, doi: 10.1016/j.actamat.2014.10.036. DOI URL
[33]	T.M. Pollock, A.S. Argon, Acta Metall. Mater. 42 (6) (1994) 1859-1874, doi: 10.1016/0956-7151(94)90011-6. DOI URL
[34]	N. Matan, D. Cox, C. Rae, R. Reed, Acta Mater. 47 (7) (1999) 2031-2045, doi: 10.1016/S1359-6454(99)00093-2. DOI URL
[35]	T.M. Pollock, S. Tin, J. Propul. Power 22 (2) (2006) 361-374, doi: 10.2514/1.18239. DOI URL
[36]	J. Zhang, T. Murakumo, Y. Koizumi, T. Kobayashi, H. Harada, S. Masaki, Metall. Mater. Trans. A 33 (12) (2002) 3741-3746, doi: 10.1007/s11661-002-0246-7. DOI URL
[37]	J.X. Zhang, T. Murakumo, Y. Koizumi, H. Harada, J. Mater. Sci. 38 (24) (2003) 4883-4888, doi: 10.1023/B:JMSC.0000004409.70156.6a. DOI URL
[38]	J.X. Zhang, T. Murakumo, H. Harada, Y. Koizumi, Scr. Mater. 48 (3) (2003) 287-293, doi: 10.1016/S1359-6462(02)00379-2. DOI URL
[39]	J.X. Zhang, J. Wang, H. Harada, Y. Koizumi, Acta Mater. 53 (17) (2005) 4623-4633, doi: 10.1016/j.actamat.2005.06.013. DOI URL
[40]	A. Epishin, T. Link, Philos. Mag. 84 (19) (2004) 1979-2000, doi: 10.1080/14786430410001663240. DOI URL
[41]	J.X. Zhang, T. Murakumo, Y. Koizumi, T. Kobayashi, H. Harada, Acta Mater. 51 (17) (2003) 5073-5081, doi: 10.1016/S1359-6454(03)00355-0. DOI URL
[42]	S. Antonov, Y. Zheng, J.M. Sosa, H.L. Fraser, J. Cormier, P. Kontis, B. Gault, Scr. Mater. 186 (2020) 287-292, doi: 10.1016/j.scriptamat.2020.05.004. DOI URL
[43]	PP. Kontis, Z. Li, D.M. Collins, J. Cormier, D. Raabe, B. Gault, Scr.Mater. 145 (2018) 76-80, doi: 10.1016/j.scriptamat.2017.10.005. DOI
[44]	F.R. Nabarro, Metall. Mater. Trans. A 27 (3) (1996) 513-530, doi: 10.1007/BF02648942. DOI URL
[45]	J.B. le Graverend, J. Cormier, M. Jouiad, F. Gallerneau, P. Paulmier, F. Hamon, Mater. Sci. Eng. A 527 (20) (2010) 5295-5302, doi: 10.1016/j.msea.2010.04.097. DOI URL
[46]	Q.Y. Huang, H.K. Li, Superalloy, Metallurgical Industry Press, Beijing, 2000.
[47]	J.T. Guo, Materials Science and Engineering for Superalloys (I), Science Press, Beijing, 2008.
[48]	J.X. Zhang, T. Murakumo, H. Harada, Y. Koizumi, T. Kobayashi, in: K.A. Green, T.M. Pollock, H. Harada, T.E. Howson, R.C. Reed, J.J. Schirra (Eds.), Superalloys 2004: Proceedings of the 10th Intenational Symposium of Superalloys, John Wiley & Sons, Inc. Hoboken, NJ, USA, 2004, pp. 189-195.
[49]	J.S. Zhang, High Temperature Deformation and Fracture of Materials, Beijing, Science Press, Beijing, 2007.
[50]	X.F. Yuan, J.T. Wu, J.T. Li, W. Li, J.C. Zhao, P. Yan, Mater. Sci. Eng. A 743 (2019) 40-56, doi: 10.1016/j.msea.2018.11.027. DOI URL
[51]	Q.Y. Li, S.G. Tian, H.C. Yu, N. Tian, Y. Su, Y. Li, Mater. Sci. Eng. A 633 (2015) 20-27, doi: 10.1016/j.msea.2015.02.056. DOI URL
[52]	A. Ibanez, V. Srinivasan, A. Saxena, Fatigue Fract. Eng. Mater. Struct. 29 (12) (2006) 1010-1020, doi: 10.1111/j.1460-2695.2006.01066.x. DOI URL
[53]	L.M. Suave, A.S. Muñoz, A. Gaubert, G. Benoit, L. Marcin, P. Kontis, P. Vil-lechaise, J. Cormier, Metall. Mater. Trans. A 49 (9) (2018) 4012-4028, doi: 10.1007/s11661-018-4708-y. DOI URL
[54]	P. Kontis, Z. Li, M. Segersäll, J.J. Moverare, R.C. Reed, D. Raabe, B. Gault, Metall. Mater. Trans. A 49 (9) (2018) 4236-4245, doi: 10.1007/s11661-018-4709-x. DOI URL
[55]	L.R. Liu, T. Jin, N.R. Zhao, Z. Wang, X. Sun, H. Guan, Z. Hu, Mater. Sci. Eng. A 385 (1-2) (2004) 105-112, doi: 10.1016/j.msea.2004.06.003. DOI URL
[56]	S.L. He, Y.S. Zhao, F. Lu, J. Zhang, L.F. Li, Q. Feng, Acta Metall. Sin. 56 (9) (2020), doi: 10.11900/0412.1961.2020.00020. DOI
[57]	Y.S. Zhao, J. Zhang, F.Y. Song, M. Zhang, Y.S. Luo, H. Zhao, D.Z. Tang, Prog. Natl. Sci. Mater. Int. 30 (3) (2020) 371-381, doi: 10.1016/j.pnsc.2020.05.003. DOI URL
[58]	Y.S. Zhao, J. Zhang, Y.S. Luo, J. Li, D.Z. Tang, Mater. Sci. Eng. A 672 (2016) 143-152, doi: 10.1016/j.pnsc.2020.05.003. DOI URL
[59]	P.J. Zhou, J.J. Yu, X.F. Sun, H.R. Guan, Z.Q. Hu, Mater. Sci. Eng. A 491 (1-2) (2008) 159-163, doi: 10.1016/j.msea.2008.02.019. DOI URL
[60]	Z.H. Zhou, B.D. Zhu, Mater. Eng. (02) (1995) 45-47.
[61]	Academic Committee of the Superalloys (CSM), China Superalloys Handbook Standards Press of China, Beijing, 2012.