Austenite carbon enrichment and decomposition during quenching and tempering of high silicon high carbon bearing steel

G. G. Ribamar*, J. D. Escobar, A. Kwiatkowski da Silva, N. Schell, J. A. Ávila, A. S. Nishikawa, J. P. Oliveira, H. Goldenstein

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

The addition of Si to steels is a well stablished method to delay cementite precipitation, allowing for carbon partitioning from martensite to retained austenite during tempering. It has been argued that carbon enrichment and stabilization of austenite leads to increased ductility and toughness. This has been the main motivation for the development of novel heat treatments, such as quenching and partitioning. High carbon steels can also benefit from improved ductility provided by the presence of stabilized retained austenite. However, the process of carbon partitioning is less understood due to the increased tendency for competitive carbide formation with increasing carbon content. The present work investigates the austenite carbon partitioning and austenite decomposition phenomena in a modified 1.82 wt.% Si hypereutectoid bearing steel during tempering. Dilatometry, in-situ and ex-situ synchrotron X-ray diffraction, 3D atom probe tomography, scanning electron microscopy, and hardness measurements were used. The results are discussed based on different equilibrium states between α' and carbides. It was found that carbon partitioning towards retained austenite occurs for several minutes without significant phase decomposition at temperatures lower than 300 °C. A transition temperature between prevalent austenite carbon enrichment and austenite decomposition occurs at 350 °C. Secondary cementite precipitation inside martensite, and at the α'/γ interfaces, is observed during tempering at temperatures above 400 °C. Results from constrained carbon equilibrium modeling with carbide presence indicate that homogeneously dispersed spheroidized primary cementite has little influence in the carbon partitioning phenomenon.

Original languageEnglish
Article number118742
Number of pages11
JournalActa Materialia
Volume247
DOIs
Publication statusPublished - 2023

Bibliographical note

Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care
Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Keywords

  • Austenite stabilization
  • Carbon partitioning
  • Microstructure
  • Quenching and tempering
  • Synchrotron radiation

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