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Isothermal transformation of austenite to ferrite and precipitation behavior in 9Cr-1.5Mo-1.25Co-0.1C-VNb heat-resistant steel

Title
Isothermal transformation of austenite to ferrite and precipitation behavior in 9Cr-1.5Mo-1.25Co-0.1C-VNb heat-resistant steel
Authors
Moon, JoonohLee, Tae-HoKim, Sung-DaeLee, Chang-HoonJang, Jae HoonShin, Jong-HoLee, Jong-WookLee, Bong HoSuh, Dong-Woo
Issue Date
2020-12
Citation
Materials Characterization, 170, 110677
Type
Article
Article Type
Article
Author Keywords
Heat-resistant steelIsothermal transformationPrior austenite grain sizeDiscontinuous precipitationM-23(C,B)(6)Interphase precipitation
Keywords
Binary alloysCarbidesChromium alloysChromium steelCobalt alloysIsothermsFerriteMolybdenum alloysMolybdenum steelNiobium alloysPrecipitation (chemical)Vanadium steelAustenite-to-ferrite transformationAustenitization temperaturesInterphase precipitationIsothermal transformationsPrecipitation behaviorPrior austenite grain boundariesPrior austenite grain sizeReheating temperatureAusteniteGrain boundariesIsothermal annealing
ISSN
1044-5803
Abstract
This study explored the transformation of austenite to ferrite and precipitation behavior during the isothermal annealing of heat-resistant steel based on Fe-9Cr-1.5Mo-1.25Co-0.1C-0.2 V-0.05Nb (wt%). For this purpose, the samples used here were initially reheated to the full austenitization temperature and thereafter directly annealed at 710 °C and 730 °C, a temperature range in which the transformation to ferrite takes place, for up to 196 h. In addition, we modified the prior austenite grain size (PAGS) by changing the reheating temperature and then analyzed the effect of PAGS on the kinetics of the isothermal transformation to ferrite. In the early stage of annealing, Cr-enriched M23(C,B)6 carbides initially precipitated along the prior austenite grain boundaries (PAGB). As annealing progressed, the ferrite began to nucleate at the PAGB and then grew into the austenite. The initial stage of the transformation to ferrite was then accompanied with the cellular precipitation of M23(C,B)6 particles. Interestingly, we also found the interphase precipitation of V- and Nb-enriched MX particles resulting from the partitioning of the C concentration at the moving austenite/ferrite interface during the austenite to ferrite transformation. The transformation was finished after annealing for more than 48 h. The time taken to complete the process was prolonged with an increase in the PAGS, indicating that the kinetics of the transformation decreased with an increase in the PAGS. © 2020 Elsevier Inc.
URI
http://hdl.handle.net/20.500.11750/12737
DOI
10.1016/j.matchar.2020.110677
Publisher
Elsevier Inc.
Files:
There are no files associated with this item.
Collection:
ETC1. Journal Articles


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