Study of carbide dissolution and austenite formation during ultra–fast heating in medium carbon chromium molybdenum steel

Spyros Papaefthymiou*, Marianthi Bouzouni, Roumen H. Petrov

*Corresponding author for this work

    Research output: Contribution to journalArticleScientificpeer-review

    15 Citations (Scopus)
    121 Downloads (Pure)

    Abstract

    In this study, UltraFast Heat Treatment (UFHT) was applied to a soft annealed medium carbon chromium molybdenum steel. The specimens were rapidly heated and subsequently quenched in a dilatometer. The resulting microstructure consists of chromium-enriched cementite and chromium carbides (in sizes between 5–500 nm) within fine (nano-sized) martensitic and bainitic laths. The dissolution of carbides in austenite (γ) during ferrite to austenite phase transformation in conditions of rapid heating were simulated with DICTRA. The results indicate that fine (5 nm) and coarse (200 nm) carbides dissolve only partially, even at peak (austenitization) temperature. Alloying elements, especially chromium (Cr), segregate at austenite/carbide interfaces, retarding the dissolution of carbides and subsequently austenite formation. The sluggish movement of the austenite/carbide interface towards austenite during carbide dissolution was attributed to the partitioning of Cr nearby the interface. Moreover, the undissolved carbides prevent austenite grain growth at peak temperature, resulting in a fine-grained microstructure. Finally, the simulation results suggest that ultrafast heating creates conditions that lead to chemical heterogeneity in austenite and may lead to an extremely refined microstructure consisting of martensite and bainite laths and partially dissolved carbides during quenching.

    Original languageEnglish
    Article number646
    Number of pages17
    JournalMetals
    Volume8
    Issue number8
    DOIs
    Publication statusPublished - 2018

    Keywords

    • Bainitic ferrite
    • Dissolution
    • Martensite
    • Microstructure
    • Simulation
    • Ultra-fast heating

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