University of Oulu

Vahid Javaheri, Sakari Pallaspuro, Saeed Sadeghpour, Sumit Ghosh, Johannes Sainio, Renata Latypova, Jukka Kömi, Rapid tempering of a medium-carbon martensitic steel: In-depth exploration of the microstructure – mechanical property evolution, Materials & Design, Volume 231, 2023, 112059, ISSN 0264-1275,

Rapid tempering of a medium-carbon martensitic steel : in-depth exploration of the microstructure – mechanical property evolution

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Author: Javaheri, Vahid1; Pallaspuro, Sakari1; Sadeghpour, Saeed1;
Organizations: 1Materials and Mechanical Engineering, Center of Advanced Steel Research, University of Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 10.3 MB)
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Language: English
Published: Elsevier, 2023
Publish Date: 2023-09-25


Rapid tempering is a remarkable sustainable and energy-efficient way to modify properties of as-quenched martensite, particularly its toughness and ductility. In this work, tensile and fracture toughness properties, and microstructural evolution of a medium-carbon (0.4 wt%), low-alloy steel under different rapid tempering circumstances are discussed. The hot-rolled and direct-quenched specimens were subjected to rapid tempering treatments (heating rate of about 90 °C/s) to the different tempering temperatures (320–720 °C). As a reference material, one sample was subjected to conventional tempering at 420 °C for one hour. The results indicated that the mechanical properties and microstructural features are influenced considerably by tempering temperature rather than the holding time. Despite the short tempering duration, the strength of tempered martensite dropped (from a max. tensile strength of ∼ 2100 MPa to a min. of ∼ 1100 MPa) while ductility increased with increasing tempering temperature (from a tensile elongation of 4% to ∼ 15%). However, the rapidly tempered sample at 420 °C experienced a loss of fracture toughness as a result of coarse stick-like cementite precipitation. Microstructural observations revealed that, even with a short time frame, tempering temperature plays a significant role in the resulting cementite morphology. At lower tempering temperatures, the cementite precipitates have a stick-like structure, while at higher temperatures, they become more globular/spheroid-like. This change in cementite morphology led to an enhancement in fracture toughness. Overall, the results indicated that, by a proper design of the rapid tempering process, an excellent combination of tensile properties and fracture toughness can be obtained compared to conventional tempering while significantly saving time and energy.

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Series: Materials & design
ISSN: 0264-1275
ISSN-E: 1873-4197
ISSN-L: 0264-1275
Volume: 231
Article number: 112059
DOI: 10.1016/j.matdes.2023.112059
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Funding: The authors would like to thank Jane ja Aatos Erkon säätiö (JAES) and Tiina ja Antti Herlinin säätiö (TAHS) for their financial supports on Advanced Steels for Green Planet project. Vahid Javaheri would also like to thank Jenny and Antti Wihuri Foundation for the personal grant and financial support.
Copyright information: © 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (