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

Autor(es)

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

• Tipo de documento: Artigo Científico
• Fonte: ACTA MATERIALIA; v. 247, p. 11-pg., 2023-02-10.

Resumo

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. Dila-tometry, in-situ and ex-situ synchrotron X-ray diffraction, 3D atom probe tomography, scanning electron mi-croscopy, and hardness measurements were used. The results are discussed based on different equilibrium states between alpha' and carbides. It was found that carbon partitioning towards retained austenite occurs for several minutes without significant phase decomposition at temperatures lower than 300 degrees C. A transition temperature between prevalent austenite carbon enrichment and austenite decomposition occurs at 350 degrees C. Secondary cementite precipitation inside martensite, and at the alpha'/gamma interfaces, is observed during tempering at tempera-tures above 400 degrees 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. (AU)

• Processo FAPESP: 18/21251-5 - Caraterização do efeito de endurecimento secundário ativado por temperatura de aços resistentes ao fogo durante a simulação de incêndios
• Beneficiário: Julian David Escobar Atehortua
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado