About this Abstract |
| Meeting |
MS&T26: Materials Science & Technology
|
| Symposium
|
Fracture of Steels: New Approaches to Modeling and Experimental Characterization
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| Presentation Title |
Synergistic Thermomechanical Fatigue Failure of a 4340 Steel Ring-Rolling Mandrel in Nickel Superalloy Forging |
| Author(s) |
Teoman M. Ekim, Alex Duke, Aiden Niemiec, Rahul Gopalakrishnan |
| On-Site Speaker (Planned) |
Teoman M. Ekim |
| Abstract Scope |
This capstone project by recent graduates of the Michigan State University Materials Science and Engineering program was conducted in collaboration with and supported by Weldaloy Specialty Forgings. A 6.5-inch diameter AISI 4340 steel mandrel used in ring rolling of nickel superalloy aerospace rings under 125-ton radial force and intermittent contact exceeding 1093°C failed after approximately three months of service. An investigation was initiated to determine root cause and provide actionable recommendations. The approach combined ultrasonic testing, macro and micro-fractography, SEM imaging, hardness mapping, microstructural characterization, and transient thermal and fracture mechanics modeling. The root cause was determined to be synergistic thermomechanical fatigue: cyclic thermal loading initiated surface cracks that were driven inward by reversed bending fatigue and accelerated by progressive thermal softening. Recommendations were provided including evaluation of alternative tool steels, thermal barrier coatings, and high-entropy alloy overlay coatings to mitigate surface crack initiation. |