Influence of the cooling rate below Ms on the martensitic transformation in a low alloy medium-carbon steel

Liu, J.H.; Binot, Nicolas; Delagnes, Denis; Jahazi, Mohammad

doi:10.1016/j.jmrt.2021.02.075

Cited by 12 publications

(5 citation statements)

References 27 publications

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“…The layer is formed down to a depth of the samples where the austenitization temperature is reached and the cooling rate v 1 equals the critical cooling rate v crit for martensitic transformation. [27][28][29] To create an underlying BEL, a second thermal load is needed, represented by a second laser surface treatment with lower laser power P Laser,2 < P Laser,1 (Figure 6(c)). The second thermal load recreates a WEL on the top part of the WEL resulting from the first thermal load and causes a tempering of the bottom part of the existing WEL that appears as a BEL in the metallographic sections.…”

Section: Discussionmentioning

confidence: 99%

Influence of thermal loading parameters and microstructure on the formation of stratified surface layers on railway wheels

Freisinger,

Pichelbauer,

Trummer

et al. 2024

Proceedings of the Institution of Mechanical Engineers, Part F:

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Due to an increasing trend towards environmentally friendly public transport, rail networks face higher speeds and wheel loads affecting the material degradation of the railway components. Within this study, influencing parameters on the formation of stratified surface layers, forming on railway wheels during service due to thermal loadings in the wheel-rail contact, are studied. These layers consist of white etching layer and underlying brown etching layer and are susceptible to fatigue crack initiation. By using laser surface treatments, its formation based on two consecutive thermal loadings is systematically demonstrated on ER7 wheel steel. Further, a decrease in layer thickness with decreasing laser power, and an increase in brown etching layer thickness with increasing laser power difference is shown. Moreover, the effect of finer grain size leading to an increased layer thickness, and the influence of the chemical composition by comparing the standard ER7 wheel steel to a micro-alloyed wheel steel are demonstrated.

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Section: Discussionmentioning

confidence: 99%

Influence of thermal loading parameters and microstructure on the formation of stratified surface layers on railway wheels

Freisinger,

Pichelbauer,

Trummer

et al. 2024

Proceedings of the Institution of Mechanical Engineers, Part F:

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“…This trend occurs because alloying elements (such as Cr and Mo) in the material increase the supercooled austenite stability. A comparison of the expansion curves under different cooling rates (figure 5) reveals that the starting point of martensitic transformation decreases as the cooling rate increases and that the end point of martensitic transformation is pushed below room temperature, resulting in incomplete martensitic transformation [18,19]. To ensure the percentage of martensitic transformation and solid solution strengthening effect, air cooling should be used for quenching.…”

Section: Structure After Quenchingmentioning

confidence: 99%

Carbide precipitation during tempering of hybrid steel 60

Zheng,

Lei,

Huang

et al. 2024

Mater. Res. Express

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The effects of carbide precipitation on mechanical performance of Hybrid Steel 60, known as a novel bearing steel, have not been investigated. In this study, the austenite transformation temperatures of Hybrid Steel 60 during heating were revealed by the thermal expansion curve. The temperature and effective activation energy of the second phase precipitation were determined by the differential scanning calorimetry (DSC) curve. Different solid solution structures after austenitization were detected using various cooling rates. The solubility temperature was determined based on hardness and residual austenite content. The carbides precipitated at the peak temperature were qualitatively identified using XRD. It was discovered that the temperature points Ac1 and Ac3 of the steel were 786 ℃ and 864 ℃, respectively. In addition, the effect of solid solution temperature on quenching hardness is minimal, while the cooling rate has a greater impact on hardness, reaching a peak at 5 ℃/s. The primary carbide phase in Hybrid Steel 60 is the M7C3 and VC. When the temperature ranges from 500 ℃ to 550 ℃, M23C6 begins to precipitate. As a result, after tempering at 525 ℃, the hardness peak value reached 566 HV.

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“…It is clearly seen that two step changes occur immediately after each other. We assume that the first step change at a temperature of 450 • C represents a bainitic transformation, and then the second step change represents a transformation to martensite at a temperature of 211 • C. This temperature representing Ms is slightly lower compared to cooling at a rate of 100 • C/s; the phenomenon accompanying the drop in Ms temperature with decreasing temperature is described in more detail in the literature [66,67]. The simulated proportion of phase fractions provides a more detailed overview of the individual phases' ratio in the resulting microstructure (Figure 9c).…”

Section: Dilatation Curves Analysismentioning

confidence: 99%

Microstructural Changes and Determination of a Continuous Cooling Transformation (CCT) Diagram Using Dilatometric Analysis of M398 High-Alloy Tool Steel Produced by Microclean Powder Metallurgy

et al. 2023

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The paper deals with the dilatometric study of high-alloy martensitic tool steel with the designation M398 (BÖHLER), which is produced by the powder metallurgy process. These materials are used to produce screws for injection molding machines in the plastic industry. Increasing the life cycle of these screws leads to significant economic savings. This contribution focuses on creating the CCT diagram of the investigated powder steel in the range of cooling rates from 100 to 0.01 °C/s. JMatPro® API v7.0 simulation software was used to compare the experimentally measured CCT diagram. The measured dilatation curves were confronted with a microstructural analysis, which was evaluated using a scanning electron microscope (SEM). The M398 material contains a large number of carbide particles that occur in the form of M7C3 and MC and are based on Cr and V. EDS analysis was used to evaluate the distribution of selected chemical elements. A comparison of the surface hardness of all samples in relation to the given cooling rates was also carried out. Subsequently, the nanoindentation properties of the formed individual phases as well as the carbides, where the nanohardness and reduced modulus of elasticity (carbides and matrix) were evaluated.

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Influence of the cooling rate below Ms on the martensitic transformation in a low alloy medium-carbon steel

Cited by 12 publications

References 27 publications

Influence of thermal loading parameters and microstructure on the formation of stratified surface layers on railway wheels

Influence of thermal loading parameters and microstructure on the formation of stratified surface layers on railway wheels

Carbide precipitation during tempering of hybrid steel 60

Microstructural Changes and Determination of a Continuous Cooling Transformation (CCT) Diagram Using Dilatometric Analysis of M398 High-Alloy Tool Steel Produced by Microclean Powder Metallurgy

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