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The nucleation and growth of η phase in nickel-based superalloy during long-term thermal exposure
Acta Materialia, Volume: 185, Pages: 493 - 506
Swansea University Author:
Soran Birosca
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DOI (Published version): 10.1016/j.actamat.2019.12.038
Abstract
The microstructure degradation and subsequent phase transformations in Waspaloy nickel-based superalloy during thermal exposure at 780 °C for 10,000 h were investigated. Two paths of η phase formation in the centre of extra-large γ’ (EL-γ’) following the formation of EL-γ’ were observed: (i) η phase...
| Published in: | Acta Materialia |
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| ISSN: | 1359-6454 |
| Published: |
Elsevier BV
2020
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| Online Access: |
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| URI: | https://cronfa.swan.ac.uk/Record/cronfa53128 |
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| Abstract: |
The microstructure degradation and subsequent phase transformations in Waspaloy nickel-based superalloy during thermal exposure at 780 °C for 10,000 h were investigated. Two paths of η phase formation in the centre of extra-large γ’ (EL-γ’) following the formation of EL-γ’ were observed: (i) η phase directly precipitated within EL-γ’ when the coalescence of γ’ reached a critical stage; (ii) η phase precipitated at the interface of small size MC carbide and EL-γ’, with both MC and η embedded inside EL-γ’. The phase transformation process including the formation of EL-γ’ were experimentally observed and the formation sequences were schematically suggested. Two criteria of η formation and growth within EL-γ’ were established: (i) stacking faults formation in the nucleation site and (ii) sufficient atom diffusion during nuclei growth. The study of kinetics of η formation through two different paths revealed the critical role of small size carbides in promoting η nucleation and growth. It is concluded that η formation may be suppressed by controlling the size and density of MC carbides during materials processing. |
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| Keywords: |
Nickel-based superalloy, η phase, MC-carbide, Phase transformation, Waspaloy |
| Start Page: |
493 |
| End Page: |
506 |