Microstructure evolution and deformation mechanisms of service-exposed P91 steel via interrupted uniaxial creep tests at 660 °C

Bonetti, R.; Neate, N.C.; Morris, A.; Shipway, P.H.; Sun, W.

Abstract

Creep degradation behaviour of service-exposed P91 steel is evaluated during interrupted creep tests at 660 °C and 80 MPa using a number of material characterization techniques including transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), energy dispersive spectroscopy (EDS) and optical microscopy (OM) to identify the microstructural evolution and the associated deformation mechanisms. Microhardness has also been measured in order to evaluate the softening mechanism. Under the creep conditions examined, microstructural degradation is found to be governed by the disappearance of the lath sub-structure, lath widening and recrystallization, as well as dislocation density reduction, coarsening of M23C6 and creep cavitation while MX and Laves phases are stable. Hardness evolution, extrapolated from hardness data obtained from uniaxial creep tests, is used to characterize the softening of the material. On this basis, hardness decrease is justified in term of the aforementioned microstructural changes. Implications of the findings for specific in-service life management in thermal plant piping systems are addressed.

Citation

Bonetti, R., Neate, N., Morris, A., Shipway, P., & Sun, W. (2024). Microstructure evolution and deformation mechanisms of service-exposed P91 steel via interrupted uniaxial creep tests at 660 °C. Journal of Materials Research and Technology, 33, 3529-3549. https://doi.org/10.1016/j.jmrt.2024.10.045

• Journal Article Type: Article
• Acceptance Date: Oct 6, 2024
• Online Publication Date: Oct 11, 2024
• Publication Date: 2024-11
• Deposit Date: Mar 5, 2025
• Publicly Available Date: Mar 5, 2025
• Journal: Journal of Materials Research and Technology
• Print ISSN: 2238-7854
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 33
• Pages: 3529-3549
• DOI: https://doi.org/10.1016/j.jmrt.2024.10.045
• Keywords: P91 steel; Interrupted creep tests; Microstructure evolution; Softening mechanism; Hardness and life fraction
• Public URL: https://nottingham-repository.worktribe.com/output/40706232
• Publisher URL: https://www.sciencedirect.com/science/article/pii/S2238785424023159
• Additional Information: This article is maintained by: Elsevier; Article Title: Microstructure evolution and deformation mechanisms of service-exposed P91 steel via interrupted uniaxial creep tests at 660 °C; Journal Title: Journal of Materials Research and Technology; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.jmrt.2024.10.045; Content Type: article; Copyright: © 2024 The Authors. Published by Elsevier B.V.