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Creep behavior of a γ′-strengthened Co-base alloy with zero γ/γ′-lattice misfit at 800 °C, 196 MPa

  • Jan Midtlyng (a1), Alexander I. Epishin (a1), Nikolay V. Petrushin (a2), Thomas Link (a1), Gert Nolze (a3), Igor L. Svetlov (a2) and Walter Reimers (a1)...

Deformation and structural behavior of an experimental γ′-strengthened Co-base alloy during creep at 800 °C and 196 MPa have been investigated. The characteristic features of this alloy are zero γ/γ′-lattice misfit and a fine γ/γ′-microstructure. In the initial condition, the γ′-precipitates in this alloy are small (size of about 100 nm), have polyhedral morphology, and are separated by the very narrow γ-channels (width of about 10 nm). The tests performed up to about 1% creep strain (about 500 h creep time) gave creep curves with a slow constant strain rate and without an apparent transient creep, typical for superalloys with nonzero misfit. In this initial stage of creep, entering of the narrow γ-channels by dislocations is blocked by a strong Orowan force. The micromechanism of creep was identified as an octahedral glide of 〈011〉 superdislocations simultaneously in two phases, γ and γ′. The γ/γ′-microstructure with zero misfit shows no rafting but rapidly coarsens isotropically. It is concluded that zero misfit is beneficial at the initial stages of the creep but is unfavourable for long-term creep because of the continuous microstructural coarsening.

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1. Sato J., Omori T., Oikawa K., Ohnuma I., Kainuma R., and Ishida K.: Cobalt-base high-temperature alloys. Science 312(5770), 90 (2006).
2. Pollock T.M., Dibbern J., Tsunekane M., Zhu J., and Suzuki A.: New Co-based high-temperature alloys. JOM 62(1), 58 (2010).
3. Suzuki A. and Pollock T.M.: High-temperature strength and deformation of γ/γ′ two-phase Co–Al–W-base alloys. Acta Mater. 56(6), 1288 (2008).
4. Bauer A., Neumeier S., Pyczak F., Singer R.F., and Göken M.: Creep properties of different γ′-strengthened Co-base superalloys. Mater. Sci. Eng., A 550, 333 (2012).
5. Bauer A., Neumeier S., Pyczak F., and Göken M.: Microstructure and creep strength of different γ/γ′-strengthened Co-base superalloy variants. Scr. Mater. 63(12), 1197 (2010).
6. Shinagawa K., Omori T., Oikawa K., Kainuma R., and Ishida K.: Ductility enhancement by boron addition in Co–Al–W high-temperature alloys. Scr. Mater. 61(6), 612 (2009).
7. Petrushin N., Hvatzkiy K., Gerasimov V., Link T., Epishin A., Nolze G., and Gerstein G.: A single-crystal Co-base superalloy strengthened by γ′ precipitates: Structure and mechanical properties. Adv. Eng. Mater. 17(6), 755 (2015).
8. Titus M.S., Suzuki A., and Pollock T.M.: Creep and directional coarsening in single crystals of new γ–γ′ cobalt-base alloys. Scr. Mater. 66(8), 503 (2012).
9. Lopez-Galilea I., Zenk C., Neumeier S., Huth S., Theisen W., and Göken M.: The thermal stability of intermetallic compounds in an as-cast SX Co-base superalloy. Adv. Eng. Mater. 17(6), 741 (2015).
10. Epishin A.I., Petrushin N.V., Link T., Nolze G., Loshchinin Y.V., and Gerstein G.: Thermal stability of the structure of a heat-resistant cobalt alloy hardened with intermetallic γ′-precipitates. Russ. Metall. 2016(4), 286 (2016).
11. Klein L., Bauer A., Neumeier S., Görken M., and Virtanen S.: High temperature oxidation of γ/γ′-strengthened Co-base superalloys. Corros. Sci. 53, 2027 (2011).
12. Pyczak F., Bauer A., Göken M., Neumeier S., Lorenz U., Oehring M., Schell N., Schreyer A., Stark A., and Symanzik F.: Plastic deformation mechanisms in a crept L12 hardened Co-base superalloy. Mater. Sci. Eng., A 571, 13 (2013).
13. Eggeler Y.M., Titus M.S., Suzuki A., and Pollock T.M.: Creep deformation-induced antiphase boundaries in L12-containing single-crystal cobalt-base superalloys. Acta Mater. 77, 352 (2014).
14. Titus M.S., Eggeler Y.M., Suzuki A., and Pollock T.M.: Creep-induced planar defects in L12-containing Co- and CoNi-base single-crystal superalloys. Acta Mater. 82, 530 (2015).
15. Eggeler Y.M., Müller J., Titus M.S., Suzuki A., Pollock T.M., and Spiecker E.: Planar defect formation in the γ′ phase during high temperature creep in single crystal CoNi-base superalloys. Acta Mater. 113, 335 (2016).
16. Brückner U., Epishin A., and Link T.: Local X-ray diffraction analysis of the structure of dendrites in single-crystal nickel-base superalloys. Acta Mater. 45(2), 5223 (1997).
17. Mughrabi H.: The importance of sign and magnitude of γ/γ′ lattice misfit in superalloys with special reference to the new γ′-hardened cobalt-base superalloys. Acta Mater. 81, 21 (2014).
18. Gao S., Fivel M., Ma A., and Hartmaier A.: Influence of misfit stresses on dislocation glide in single crystal superalloys: A three-dimensional discrete dislocation dynamics study. J. Mech. Phys. Solids 76, 276 (2015).
19. Hemmersmeier U. and Feller-Kniepmeier M.: Element distribution in the macro- and microstructure of nickel base superalloy CMSX-4. Mater. Sci. Eng., A 248, 87 (1998).
20. Schulze C. and Feller-Kniepmeier M.: Transmission electron microscopy of phase composition and lattice misfit in the Re-containing nickel-base superalloy CMSX-10. Mater. Sci. Eng., A 281, 204 (2000).
21. Kurdjumov G. and Sachs G.: Über den Mechanismus der Stahlhärtung. Z. Phys. 64(5), 325 (1930).
22. Nolze G.: Characterization of the fcc/bcc orientation relationship by EBSD using pole figures and variants. Z. Metallkd. 95, 744 (2004).
23. Socrate S. and Parks D.M.: Numerical determination of the elastic driving force for directional coarsening in Ni-superalloys. Acta Metall. Mater. 41(7), 2185 (1993).
24. Nabarro F.R.N.: Rafting in superalloys. Metall. Mater. Trans. A 27(3), 513 (1996).
25. Brückner U., Epishin A., Link T., and Dressel K.: The influence of the dendritic structure on the γ/γ′-lattice misfit in the single-crystal nickel-base superalloy CMSX-4. Mater. Sci. Eng., A 247(1–2), 23 (1998).
26. Report on DFG Project: Characterisation of the quaternary system Co–Al–W–Ta for development of γ′-strengthened Co-base alloys, EP 136/2–1, NO 307/5-1, TU Berlin, BAM Berlin, VIAM Moscow (2016).
27. Link T., Epishin A., and Fedelich B.: Inhomogeneity of misfit stresses in nickel-base superalloys: Effect on propagation of matrix dislocation loops. Philos. Mag. 89(13), 1141 (2009).
28. Feller-Kniepmeier M. and Link T.: Dislocation structures in γ–γ′ interfaces of the single-crystal superalloy SRR 99 after annealing and high temperature creep. Mater. Sci. Eng., A 113, 191 (1989).
29. Probst-Hein M., Dlouhy A., and Eggeler G.: Interface dislocations in superalloy single crystals. Acta Mater. 47(8), 2497 (1999).
30. Carrol L.J., Feng Q., and Pollock T.M.: Interfacial dislocation networks and creep in directionally coarsened Ru-containing nickel-base single-crystal superalloys. Metall. Mater. Trans. A 39, 1290 (2008).
31. Zhang J.X., Harada H., Koizumi Y., and Kobayashi T.: Dislocation motion in the early stages of high-temperature low-stress creep in a single-crystal superalloy with a small lattice misfit. J. Mater. Sci. 45(2), 523 (2010).
32. Kear B.H. and Wilsdorf H.G.F.: Dislocation configurations in plastically deformed polycrystalline Cu3Au alloys. Trans. AIME 224, 382 (1962).
33. Scheumann-Frerker G., Gabrisch H., and Feller-Kniepmeier M.: Dislocation microstructures in a single-crystal nickel-base superalloy after tensile testing at 823 K in the [001] direction. Philos. Mag. 65(6), 1353 (1992).
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Journal of Materials Research
  • ISSN: 0884-2914
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