Print Email Facebook Twitter Study of carbide dissolution and austenite formation during ultra–fast heating in medium carbon chromium molybdenum steel Title Study of carbide dissolution and austenite formation during ultra–fast heating in medium carbon chromium molybdenum steel Author Papaefthymiou, Spyros (National Technical University of Athens) Bouzouni, Marianthi (National Technical University of Athens; Hellenic Research Centre for Metals S.A. -ELKEME S.A.) Petrov, R.H. (TU Delft (OLD) MSE-3; Universiteit Gent) Date 2018 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. Subject Bainitic ferriteDissolutionMartensiteMicrostructureSimulationUltra-fast heating To reference this document use: http://resolver.tudelft.nl/uuid:7c1cc518-d222-4397-9402-f79ceb8fd505 DOI https://doi.org/10.3390/met8080646 ISSN 2075-4701 Source Metals, 8 (8) Part of collection Institutional Repository Document type journal article Rights © 2018 Spyros Papaefthymiou, Marianthi Bouzouni, R.H. Petrov Files PDF metals_08_00646_v3.pdf 2.69 MB Close viewer /islandora/object/uuid:7c1cc518-d222-4397-9402-f79ceb8fd505/datastream/OBJ/view