EBSD investigation of the crack initiation and TEM/FIB analyses of the microstructural changes around the cracks formed under Rolling Contact Fatigue (RCF)

Grabulov, A.; Petrov, Roumen; Zandbergen, H.W.

doi:10.1016/j.ijfatigue.2009.07.002

Cited by 187 publications

(190 citation statements)

References 9 publications

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“…This agrees with the findings found from the 18.5-h RCF test in [24] that found 49 NMIs and 41 rank 1 or 2 NMIs in 5 fully mapped WECs, these predominantly being small sized (~ 2-15 μm) D Dup, D DupTi(C,N) and D-type inclusions. The oxide encapsulations are responsible for hardness discrepancy with the martensite matrix, induced tensile residual stresses due to differing coefficients of thermal expansion and weak coherence/de-bonding of the oxide and matrix [9,68,69]. The majority of the inclusion-WEC interactions were recorded at a depth of ~ 50-200 μm, this being consistent with the depth of high subsurface shear stresses (τ 0, max = 92 μm, τ uni, max = 145 μm) (see Fig.…”

Section: Inclusion-wec Interactions and Steel Cleanlinesssupporting

confidence: 58%

“…The appearance of WEA is revealed when etched in nital solution (2% nitric acid in ethanol). WEA is a nanocrystalline ferrite structure of grain sizes ~ 5-300 nm, ~ 10-50% harder than the surrounding matrix and comprised of wholly or partially dissolved spherical carbides found to be part of the WEA formation process [3][4][5][6][7][8][9][10][11][12][13]. Amorphous-like phases have also been shown to be present in WEA, forming first before WEA is generated [8,14,15].…”

Section: Introductionmentioning

confidence: 99%

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The Evolution of White Etching Cracks (WECs) in Rolling Contact Fatigue-Tested 100Cr6 Steel

et al. 2017

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The formation of white etching cracks (WECs) in steel rolling element bearings can lead to the premature rolling contact fatigue (RCF) failure mode called white structure flaking. Driving mechanisms are still debated but are proposed to be combinations of mechanical, tribochemical and electrical effects. A number of studies have been conducted to record and map WECs in RCF-tested samples and bearings failed from the field. For the first time, this study uses serial sectioning metallography techniques on non-hydrogen charged test samples over a range of test durations to capture the evolution of WEC formation from their initiation to final flaking. Clear evidence for subsurface initiation at non-metallic inclusions was observed at the early stages of WEC formation, and with increasing test duration the propagation of these cracks from the subsurface region to the contact surface eventually causing flaking. In addition, an increase in the amount of associated microstructural changes adjacent to the cracks is observed, this being indicative of the crack being a prerequisite of the microstructural alteration.

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Section: Inclusion-wec Interactions and Steel Cleanlinesssupporting

confidence: 58%

Section: Introductionmentioning

confidence: 99%

The Evolution of White Etching Cracks (WECs) in Rolling Contact Fatigue-Tested 100Cr6 Steel

et al. 2017

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“…4.1, it should be noted that small amounts of water in the oil can generate sufficient amounts of hydrogen. Therefore, without measuring the water content in the oil it is unknown whether small amounts of water are present and that significant amounts of hydrogen were also generated through tribochemical reactions with water [3]. It is, however, also reported that when water is present, hydrogen predominantly derives from the oil opposed to the water [62].…”

Section: Tda Relation To Wec Formationsmentioning

confidence: 99%

“…One of these suggested drivers is hydrogen, where hydrogen that is either sourced from the lubricant or water contamination is released during operation and diffuses into the bearing steel, diffusion of hydrogen leading to an 'embrittlement' of the steel and promoting WEC formations [1][2][3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Thermal Desorption Analysis of Hydrogen in Non-hydrogen-Charged Rolling Contact Fatigue-Tested 100Cr6 Steel

et al. 2017

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Hydrogen diffusion during rolling contact fatigue (RCF) is considered a potential root cause or accelerator of white etching cracks (WECs) in wind turbine gearbox bearing steels. Hydrogen entry into the bearing steel during operation is thought to occur either through the contact surface itself or through cracks that breach the contact surface, in both cases by the decomposition of lubricant through catalytic reactions and/or tribochemical reactions of water. Thermal desorption analysis (TDA) using two experimental set-ups has been used to measure the hydrogen concentration in non-hydrogen-charged bearings over increasing RCF test durations for the first time. TDA on both instruments revealed that hydrogen diffused into the rolling elements, increasing concentrations being measured for longer test durations, with numerous WECs having formed. On the other hand, across all test durations, negligible concentrations of hydrogen were measured in the raceways, and correspondingly no WECs formed. Evidence for a relationship between hydrogen concentration and either the formation or the acceleration of WECs is shown in the rollers, as WECs increased in number and severity with increasing test duration. It is assumed that hydrogen diffusion occurred at wear-induced nascent surfaces or areas of heterogeneous/patchy tribofilm, since most WECs did not breach the contact surface, and those that did only had very small crack volumes for entry of lubricant to have occurred.

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“…It has been observed that subsurface plastic deformation damage in bearings are often associated with butterfly cracking at the white etch area (WEA) [11]. WEA is a region associated with nano-recrystallised carbide-free ferrite [12].…”

Section: Introductionmentioning

confidence: 99%

Mapping of axial plastic zone for roller bearing overloads using neutron transmission imaging

et al. 2018

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Article HIGHLIGHTS• A loading frame was designed to simulate bearing overloads on the ENGIN-X strain diffractometer at ISIS neutron source, UK.• Neutron transmission imaging was used to map a Bragg edge fitting parameter, associated with material yielding.• It was demonstrated that bearing overloads generate regions of subsurface plasticity in overloaded roller bearings.• Subsurface deformation, observed during roller bearing overload events, appears to reduce the bearings life expectancy. Premature failure of wind turbine gearbox bearings is an ongoing concern for industry, with sudden overload events potentially contributing towards raceway damage, significantly hindering performance. Subsurface stresses generated along a line contact cause material yielding, and a probable crack initiation site. Currently, the ability to study subsurface plastic zone evolution using non-destructive techniques is limited. Neutron Bragg edge imaging is a novel technique, allowing for two-dimensional mapping of the Bragg edge broadening parameter, indicative of bulk plastic deformation. An experiment on the ENGIN-X strain scanning instrument, at the ISIS neutron source, UK, was setup for Bragg edge transmission imaging, to measure the effect of in situ loading on the raceway of a bearing, scaled-down from a traditional wind turbine gearbox bearing. Results demonstrate a strong correlation between load and the Bragg edge width, and allow for future experimental development in studying, not only the effect of overloads on fatigue life, but also the use of neutron imaging for evaluating plastic deformation in engineering components. GRAPHICAL ABSTRACT abstract article info

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EBSD investigation of the crack initiation and TEM/FIB analyses of the microstructural changes around the cracks formed under Rolling Contact Fatigue (RCF)

Cited by 187 publications

References 9 publications

The Evolution of White Etching Cracks (WECs) in Rolling Contact Fatigue-Tested 100Cr6 Steel

The Evolution of White Etching Cracks (WECs) in Rolling Contact Fatigue-Tested 100Cr6 Steel

Thermal Desorption Analysis of Hydrogen in Non-hydrogen-Charged Rolling Contact Fatigue-Tested 100Cr6 Steel

Mapping of axial plastic zone for roller bearing overloads using neutron transmission imaging

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