Influence of chemical segregation on bainitic microstructures in a carburized bearing steel

J. Abraham Mathews*, J. Sietsma, R. H. Petrov, M. J. Santofimia

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

1 Citation (Scopus)
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Bainite to austenite reversal is one of the grain refinement techniques employed in carburized steels. However, chemical segregation influences the homogeneity of the bainitic structure, which is seminal to exploit the advantages associated with austenite reversal. It is therefore important to understand the influence of chemical segregation on bainite formation, which is investigated in this work. Characterizations were performed on the microstructures obtained from the case and core regions of a carburized steel after 30 h of bainite treatment at 320 °C for two carbon compositions: 0.85 wt% C (zcase) and 0.16 wt% C (zcore). The microstructure of zcase is shown to contain bands with bainite in alloy-lean regions and martensite/austenite in alloy-rich regions. For zcore, although the chemical bands are not composed of different phases, the alloy-rich regions have a fraction of martensite-austenite (MA) islands that is twice the fraction in alloy-lean regions. Despite this difference, the austenite phase fractions in the chemical bands of zcore are low and almost similar, indicating that the MA islands are mostly martensite. From experimental results and thermodynamic and kinetic simulations, it is elucidated that a different rate of phase transformation in the chemical bands is the cause for the observed microstructural inhomogeneities.

Original languageEnglish
Article number111232
Number of pages12
JournalMaterials and Design
Publication statusPublished - 2022


  • Bainite formation
  • Carburized steels
  • Chemical segregation
  • Microstructural bands


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