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Understanding Creep Deformation and Lifing Approaches for Advanced Nickel and Steel Alloys / MEIHUI CHONG
Swansea University Author: MEIHUI CHONG
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Copyright: The author, Meihui Chong, 2025 Distributed under the terms of a Creative Commons Attribution 4.0 License (CC BY 4.0)
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DOI (Published version): 10.23889/SUThesis.71056
Abstract
This study explores the creep behaviour of three polycrystalline alloys—stainless steel 316, Haynes 282, and Inconel 713C—chosen for their varying precipitate volume fractions. The primary aim is to provide a comprehensive understanding of the underlying mechanisms that control creep behaviour in th...
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Swansea
2025
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| Supervisor: | Whittaker, M., and Davies, H. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa71056 |
| Abstract: |
This study explores the creep behaviour of three polycrystalline alloys—stainless steel 316, Haynes 282, and Inconel 713C—chosen for their varying precipitate volume fractions. The primary aim is to provide a comprehensive understanding of the underlying mechanisms that control creep behaviour in these alloys, with a particular focus on determining the creep activation energies (Qc*) involved.SS316 displays a gradual transition in Qc* values (153–298 kJ/mol; up to 305 kJ/mol for plates), attributed to dislocation movement at low temperatures and twinning above yield stress at elevated conditions. Haynes 282 shows a wider range (276–427 kJ/mol),with γ′ precipitate resistance at low stress and forest hardening above yield strength.In contrast, Inconel 713C with highest volume fraction of precipitates, exhibits a constant Qc*, indicating creep governed by confined dislocation motion within γchannels, with no clear transition.To further examine deformation behaviour in SS316, cyclic creep tests were conducted between 600 °C/334 MPa and 700 °C/165 MPa. The results indicate that cyclic creep reduces the material’s service life and that the transition from dislocation cell formation to twin boundary formation contributes to an increased creep rate as the temperature rises from 600 °C to 700 °C. Additionally, when cycling from 700 °C to 600 °C, the creep rate was found to be higher than expected. This may be attributed to the retrograde formation of dislocations during the recovery phase, which are rapidly disrupted upon reloading.The findings reinforce the utility of the Wilshire equations in rationalising Qc* values and linking them to microstructural mechanisms. This provides a robust framework for predicting creep behaviour, aiding alloy development and high-temperature material optimisation. |
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| Keywords: |
Creep, Wilshire equations, Activation energy, Stainless steel 316, Haynes 282, Inconel 713C |
| College: |
Faculty of Science and Engineering |