Time-dependent synchrotron X-ray diffraction on the austenite decomposition kinetics in SAE 52100 bearing steel at elevated temperatures under tensile stress

Jimenez-Melero, Enrique; Blondé, R.; Sherif, Mohamed Y.; Honkimäki, V.; Dijk, NH van

doi:10.1016/j.actamat.2012.10.025

Cited by 32 publications

(33 citation statements)

References 49 publications

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“…for transformations in steels [35,36] and ceramic coatings [37], to extract kinetic information about phase transformations from experimental data is the KJMA equation [38][39][40][41]. The equation is presented in its differential form in Eq.…”

Section: Kinetic Analysismentioning

confidence: 99%

In situ X-ray scattering study of the cubic to hexagonal transformation of AlN in Ti1−xAlxN

et al. 2014

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In the present work, we have studied the decomposition of arc-evaporated Ti 0.55 Al 0.45 N and Ti 0.36 Al 0.64 N during heat treatments in vacuum by in situ synchrotron wide-angle X-ray scattering primarily to characterize the kinetics of the phase transformation of AlN from the cubic (c) NaCl structure to the hexagonal (h) wurtzite structure. In addition, in situ small-angle X-ray scattering measurements were conducted to explore details of the wavelength evolution of the spinodal decomposition, thus providing information about the critical size of the c-AlN-rich domains prior to the onset of the transformation to h-AlN. We report the fractional cubic to hexagonal transformation of AlN in Ti 1Àx Al x N as a function of time and extract activation energies between 320 and 350 kJ mol À1 depending on the alloy composition. The onset of the hexagonal transformation occurs $50 K lower in Ti 0.36 Al 0.64 N compared to Ti 0.55 Al 0.45 N where the high Al content alloy also has a significantly higher transformation rate. A critical wavelength for the cubic domains of $13 nm was observed for both alloys. Scanning transmission electron microscopy shows a c-TiN/h-AlN microstructure with a striking morphology resemblance to the c-TiN/c-AlN microstructure present prior to the hexagonal transformation.

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Section: Kinetic Analysismentioning

confidence: 99%

In situ X-ray scattering study of the cubic to hexagonal transformation of AlN in Ti1−xAlxN

et al. 2014

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“…Whilst considerable amount of evidence on retained austenite decomposition has been reported [11,12,13,19,20,21,22], early studies are limited to conventional X-ray diffraction and microscopy techniques which show only snapshots of the retained austenite transforamtion. A recent study [23] has revealed the carbon redistribution path associated with the decomposition of retained austenite using time-resolved synchrotron X-ray radiation, the study, however, focuses on retained austenite decomposition at temperatures up to ∼200 • Table 1. Whilst 100Cr6 is commonly employed for small to medium bearing applications, 100CrMnSi6-4 allows greater hardenability due to its relatively high Mn and Si contents and can be utilised for medium to large components [24].…”

Section: Introductionmentioning

confidence: 99%

Stability of retained austenite in martensitic high carbon steels. Part I: Thermal stability

Cui

Gintalas

Rivera-Dı́az-del-Castillo

2018

Materials Science and Engineering: A

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Thermal stability of retained austenite in 1C-1.5Cr steels with two Si and Mn contents is studied. Time-resolved high resolution synchrotron X-ray radiation and dilatometry are employed. The threshold transformation temperatures, decomposition kinetics, associated transformation strain, as well as the influence of Si and Mn were investigated. The coefficients of linear thermal expansion for both the bulk materials and individual phases are also obtained. The results indicate that an increase in the Mn and Si contents show little influence on the onset of retained austenite decomposition, but result in more thermally stable austenite. The decomposition is accompanied by a simultaneous increase in ferrite content which causes an expansive strain in the order of 10 −4 , and subsequent cementite development from 300-350 • C which causes a contraction that helps to neutralise the expansive strain. During decomposition, a continuous increase in the carbon content of austenite, and a reduction in that of the tempered-martensite/ferrite phase was observed. This process continued at elevated temperatures until full decomposition was reached, which could take less than an hour at a heating rate of 0.05 • C/s. Additionally, the observation of austenite peak splitting on samples with high Mn and Si contents suggests the existence of austenite of different stabilities in such matrix.

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“…Prerequisites for the KJMA equation include an infinitely large bulk with a random homogeneous nucleation. This is generally not fulfilled in most cases but owing to the simplicity of the KJMA equation it is widely used among experimentalists for transformations in, e.g., steel [25][26][27], polymers [28], and ceramic coatings [29]. Due to the prerequisites of a homogenous nucleation there are modified versions of the KJMA equation to account for grain boundary nucleation [30,31].…”

Section: Nucleation and Growthmentioning

confidence: 99%

Microstructural evolution of TiAlN hard coatings at elevated pressures and temperatures

Norrby¹

2014

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LINKÖPING 2014The cover image shows nine two-dimensional x-ray diffractograms of TiAlN merged into one quarter circle. Going counterclockwise from an as-deposited sample, the parts show different stages of annealing. The color scheme is chosen to represent the motto "Stort hjärta, hårt arbete".Niklas Norrby, unless otherwise stated ISBN: 978-91-7519-372-4 ISSN: 0345-7524 Printed by LiU-Tryck, Linköping, Sweden, 2014 i Abstract A typical hard coating on metal cutting inserts used in for example turning, milling or drilling operations is TiAlN. At elevated temperatures, TiAlN exhibits a well characterized spinodal decomposition into coherent cubic TiN and AlN rich domains, which is followed by a transformation from cubic to hexagonal AlN. Using in-situ synchrotron x-ray radiation, the kinetics of the second transformation was investigated in this thesis and the strong temperature dependence on the transformation rate indicated a diffusion based nucleation and growth mechanism. The results gave additional information regarding activation energy of the transformation and the critical wavelength of the cubic domains at the onset of hexagonal AlN. After nucleation and growth, the hexagonal domains showed a striking resemblance with the preexisting cubic AlN microstructure.During metal cutting, the tool protecting coating is subjected to temperatures of ~900 ºC and pressure levels in the GPa range. The results in this thesis have shown a twofold effect of the pressure on the decomposition steps. Firstly, the spinodal decomposition was promoted by the applied pressure during metal cutting which was shown by comparisons with annealed samples at similar temperatures. Secondly, the detrimental transformation from cubic to hexagonal AlN was shown to be suppressed at elevated hydrostatic pressures. A theoretical pressure/temperature phase diagram, validated with experimental results, also showed suppression of hexagonal AlN by an increased temperature at elevated pressures.The spinodal decomposition during annealing and metal cutting was in this work also shown to be strongly affected by the elastic anisotropy of TiAlN, where the phase separation was aligned along the elastically softer <100> directions in the crystal. The presence of the anisotropic microstructure enhanced the mechanical properties compared to the isotropic case, mainly due to a shorter distance between the c-AlN and c-TiN domains in the anisotropic case. Further improvement of the metal cutting behavior ii was realized by depositing individual layers with an alternating bias. The individual bias layers exhibited microstructural differences with different residual stress states. The results of the metal cutting tests showed an enhanced wear resistance in terms of both crater and flank wear compared to coatings deposited with a fixed bias.iii Populärvetenskaplig sammanfattningI den här avhandlingen presenteras forskningsresultat på en keramisk beläggning, TiAlN (titanaluminiumnitrid), som ligger som ett skyddande skikt på svarvskär. Tjockleken på beläggni...

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Time-dependent synchrotron X-ray diffraction on the austenite decomposition kinetics in SAE 52100 bearing steel at elevated temperatures under tensile stress

Cited by 32 publications

References 49 publications

In situ X-ray scattering study of the cubic to hexagonal transformation of AlN in Ti1−xAlxN

In situ X-ray scattering study of the cubic to hexagonal transformation of AlN in Ti1−xAlxN

Stability of retained austenite in martensitic high carbon steels. Part I: Thermal stability

Microstructural evolution of TiAlN hard coatings at elevated pressures and temperatures

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