Characteristics and Kinetics of Bainite Transformation Behaviour in a High-Silicon Medium-Carbon Steel above and below the Ms Temperature

Pashangeh, Shima; Banadkouki, S.S. Ghasemi; Somani, Mahesh C.; Kömi, Jukka

doi:10.3390/ma15020539

Cited by 6 publications

(6 citation statements)

References 46 publications

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“…Interestingly, the presence of a small fraction of martensite accelerates the isothermal bainite transformation. As found by Tian et al [30], Morawiec et al [32], Pashangeh et al [33], and Guo et al [34], due to the shear-like military transformation of martensite, a higher concentration of martensite increases the dislocation density and increases the internal stresses in the undercooled austenite, enhancing the driving force for the nucleation and transformation of bainite. Although they are both classified as military transformations, unlike martensite, bainitic transformation typically requires a nucleation period.…”

Section: Resultsmentioning

confidence: 75%

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Optimizing Hot-Work Tool Steel Microstructure for Enhanced Toughness

Bajželj,

Balaško,

Šetina Batič

et al. 2023

Crystals

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Hot-work tool steels play a crucial role in applications exposed to extreme thermal, mechanical, and chemical stresses and require exceptional properties such as high strength, hardness, wear resistance, and toughness. The latter is crucial to prevent an unexpected tool failure due to the formation and propagation of fatigue cracks in demanding environments. In addition, high thermal conductivity is crucial to prevent overheating of the tool and the resulting degradation of the material. This study focuses on a new generation hot-work tool steel with increased Mo and W contents, which has excellent thermal conductivity but limited toughness, as it contains stable Mo-W carbides that remain stable up to 1100 °C. To improve toughness, an alternative heat-treatment method involving austempering at different temperatures was applied. The investigation begins with the characterisation of the chemical composition of the steel, followed by the determination of the martensite-start (MS) and martensite-finish (Mf) temperatures. Based on the results, the researchers established a set of samples for austempering heat treatment. They investigated the effects of different isothermal holding temperatures on the microstructure of the steel and its subsequent mechanical properties. The results show that reduced bainite formation, achieved by austempering at certain temperatures, led to significantly improved impact toughness and moderate hardness. This study also showed a correlation between the isothermal holding temperature and the extent of martensitic transformation, which affected the microstructure and mechanical properties of the steel.

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Section: Resultsmentioning

confidence: 75%

“…The diffusion of carbon and other alloying elements is restricted, resulting in a fine bainitic microstructure. Martensitic grains that form during cooling below the M S temperature act as nucleation sites and accelerate the transformation into lower bainite [30,[32][33][34].…”

Section: Introductionmentioning

confidence: 99%

Optimizing Hot-Work Tool Steel Microstructure for Enhanced Toughness

Bajželj,

Balaško,

Šetina Batič

et al. 2023

Crystals

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“…7 h). Thus, the bainitic transformation time increased as the transformation temperature decreased [44]. It is well-known that the temperature of the bainite transformation affects the morphology of the structure and the degree of its refinement.…”

Section: Examination Of Phase Transformation Kinetics Based On Dilato...mentioning

confidence: 97%

Controlling the Thermal Stability of a Bainitic Structure by Alloy Design and Isothermal Heat Treatment

et al. 2023

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The aim of this work was to develop a novel bainitic steel that will be specifically dedicated to achieving a high degree of refinement (nano- or submicron scale) along with increased thermal stability of the structure at elevated temperatures. The material was characterized by improved in-use properties, expressed as the thermal stability of the structure, compared to nanocrystalline bainitic steels with a limited fraction of carbide precipitations. Assumed criteria for the expected low martensite start temperature, bainitic hardenability level, and thermal stability are specified. The steel design process and complete characteristics of the novel steel including continuous cooling transformation and time–temperature–transformation diagrams based on dilatometry are presented. Moreover, the influence of bainite transformation temperature on the degree of structure refinement and dimensions of austenite blocks was also determined. It was assessed whether, in medium-carbon steels, it is possible to achieve a nanoscale bainitic structure. Finally, the effectiveness of the applied strategy for enhancing thermal stability at elevated temperatures was analyzed.

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“…Extensive studies and diverse processing approaches have been carried out to alter the microstructure of alloy steel and improve its impact resistance, stiffness, wear resistance, and strength [7][8][9][10][11][12]. Abbasi et al analyzed the microstructural features of three different types of medium carbon steel (namely, MnCrB-, NiCrSi-, and NiCrMoV-bearing steels) and found that the addition of small amounts of alloying elements and varying austenitic grain sizes were mainly responsible for the changes in the microstructure and mechanical properties of the steel [13].…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Thermodynamic Transformation and Rare Earth Microalloying of a Medium Carbon-Medium Alloy Steel for Large Ball Mill Liners

et al. 2022

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The medium carbon-medium alloy steel was developed for the manufacture of large ball mill liners and sports equipment. In this study, the continuous cooling transformation curve of a novel type of medium carbon-medium alloy steel was measured with a thermal simulation machine; based on this curve, the hardening and tempering processes were optimized. The steel was then complex modified with alkaline earth and rare earth alloys. The mechanical properties of the treated steel were tested. The microstructure of the steel was analyzed by metallographic microscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy, and the wear surface of the steel was analyzed by a three-dimensional morphometer. After high-temperature tempering, the microstructure transformed into tempered sorbite, which possesses good mechanical properties and can adapt to working conditions that require high strength and toughness. Rare earth or alkaline earth modification of the medium carbon-medium alloy steel promoted microstructural uniformity and grain refinement and improved the mechanical and anti-wear properties.

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Characteristics and Kinetics of Bainite Transformation Behaviour in a High-Silicon Medium-Carbon Steel above and below the Ms Temperature

Cited by 6 publications

References 46 publications

Optimizing Hot-Work Tool Steel Microstructure for Enhanced Toughness

Optimizing Hot-Work Tool Steel Microstructure for Enhanced Toughness

Controlling the Thermal Stability of a Bainitic Structure by Alloy Design and Isothermal Heat Treatment

Investigation of the Thermodynamic Transformation and Rare Earth Microalloying of a Medium Carbon-Medium Alloy Steel for Large Ball Mill Liners

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