E-Thesis 194 views
Corrosion-Fatigue Study of a Novel Maraging Steel: Atmospheric and Salt Fog Effects / DEAN SCOURFIELD
Swansea University Author: DEAN SCOURFIELD
DOI (Published version): 10.23889/SUthesis.63691
Abstract
A novel maraging steel (F1E) with both high strength & toughness has been proposed to replace the Low-Pressure Turbine (LPT) shaft within the aeroengine, which is currently manufactured using two materials joined together by an inertia friction weld process. The LPT shaft is a critical component...
| Published: |
Swansea, Wales, UK
2023
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | EngD |
| Supervisor: | Jeffs, Spencer. and Rawson, Martin. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa63691 |
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| Abstract: |
A novel maraging steel (F1E) with both high strength & toughness has been proposed to replace the Low-Pressure Turbine (LPT) shaft within the aeroengine, which is currently manufactured using two materials joined together by an inertia friction weld process. The LPT shaft is a critical component in the gas turbine engine operating under extreme conditions. Ultra-high strength steels are the material of choice to endure the extensive temperature differences & mechanical loading, however, steel alloy corrosion resistance is inherently dependent on the operating environment and chemical composition. The corrosion properties of F1E are not well established akin to in-service environments and the research is limited within the area of maraging steel corrosion-fatigue. The current research aims to review the corrosion-fatigue behavior and mechanisms of F1E by conducting atmospheric trials in an ISO 9223 rated environment and investigating the effect on fatigue life, ultimately assessing corrosion and fatigue separately. In addition, F1E was investigated under salt fog corrosion conditions using 3.5% NaCl in synergy with cyclic loading, thus developing an understanding of corrosion and fatigue in synergy. Atmospheric corrosion trials were conducted up to a maximum of 36 months exposure. It is believed that increased exposure time has a detrimental effect on fatigue life due to increased localized corrosion characteristics, which act as stress raising features for crack nucleation. Salt fog fatigue tests were carried out at two conditions, one of which saw a defined pre-exposure interval (72 hours) prior to synergistic cyclic loading versus 0-hour pre-exposure.The evolution of localized corrosion in both forms of testing was examined through means of pitting depth, corrosion feature density & stress concentration (Kt). In addition, the threshold stress intensity factor for crack propagation (K1Max) was calculated by employing ‘area’ as a geometrical parameter within the field of Linear Elastic Fracture Mechanics (LEFM), which assumes small defects to be cracks. Initiating pitting characteristics were determined from the fracture surface. |
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| Item Description: |
A selection of third party content is redacted or is partially redacted from this thesis due to copyright restrictions. |
| Keywords: |
Corrosion, Fatigue, Maraging Steel, Atmospheric Corrosion, Salt Fog |
| College: |
Faculty of Science and Engineering |