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Aging Phenomena during In-Service Creep Exposure of Heat-Resistant Steels

1
Department of Mechanical Engineering, Khalifa University, Abu Dhabi 127788, UAE
2
Department of Mechanical Engineering, University of Thessaly, Volos 38334, Greece
3
Center for Catalysis and Separations, Khalifa University, Abu Dhabi 127788, UAE
*
Author to whom correspondence should be addressed.
Metals 2019, 9(7), 800; https://doi.org/10.3390/met9070800
Received: 17 June 2019 / Revised: 11 July 2019 / Accepted: 17 July 2019 / Published: 19 July 2019
(This article belongs to the Special Issue Failure Mechanisms in Alloys)
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Abstract

An investigation of aging phenomena during creep exposure has been conducted for HP-Nb cast reformer tubes for several exposure conditions. Aging was manifested by carbide precipitation, carbide coarsening, and carbide transformation. The transformation of primary M7C3 to the more stable M23C6 carbide takes place at high exposure temperature (910 °C and above). The primary MC carbides transform to the Ni-Nb silicide or G-phase during creep exposure. The presence of Ti in the steel prevented the transformation of MC carbides to the G-phase. Morphological changes like needle to globular transitions, rounding of carbide edges, and carbide coarsening take place during creep exposure. The room-temperature tensile elongation and ultimate tensile strength are significantly reduced during creep exposure. The above aging phenomena are precursors to creep damage. View Full-Text
Keywords: creep; steam reforming; carbides; G-phase; aging; cast reformer tubes creep; steam reforming; carbides; G-phase; aging; cast reformer tubes
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Haidemenopoulos, G.N.; Polychronopoulou, K.; Zervaki, A.D.; Kamoutsi, H.; Alkhoori, S.I.; Jaffar, S.; Cho, P.; Mavros, H. Aging Phenomena during In-Service Creep Exposure of Heat-Resistant Steels. Metals 2019, 9, 800.

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