Application of Complementary Techniques for Advanced Characterization of White Etching Cracks

West, Ole; Diederichs, Annika Martina; Alimadadi, Hossein; Dahl, Kristian Vinter; Somers, Marcel A. J.

doi:10.3139/147.110246

Cited by 30 publications

(50 citation statements)

References 11 publications

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“…However, it cannot be ruled out that, in accordance with new investigations, nonmetallic inclusions are somehow involved. Recent investigations using three-dimensional sectioning show, however, that nonmetallic inclusions could be involved as drivers for WECs (Evans,et al (44); West, et al (45)). There are no doubts regarding the degradation of chromium carbides, meaning that during the WEC processes specifically the carbides are under attack (see Fig.…”

Section: Wec Microstructurementioning

confidence: 97%

White Etching Crack Root Cause Investigations

Holweger

Wolf

Merk

et al. 2014

Tribology Transactions

114

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White etching crack (WEC) failure is distinct to classical fatigue and driven by the composition of lubricants under special loading conditions; for example, slippage and electricity. The white etching area (WEA) within WEC contains carbon supersaturated ferrite (bcc-iron) and carbides, with a size of a few nanometers. This article presents investigations supporting the hypothesis that WEC processes start within a failure-free period by successive accumulation of a structural distortion. This can be measured by acoustic emission. Failure statistics show a steep ascent in the Weibull diagram (ß values beyond 1) leading to the assumption that WEC processes start unsuspicious, as one would see as a failure-free period, but imply a hidden subsurface accumulation of material defects. It is suggested and supported by the evidence presented within this article that WEC is neither related to the presence of nonmetallic inclusions nor related to other impurities in the steel. Instead, the failure is a sequence and accumulation of plastic deformations in the microstructure. Within the SAE 52100 material as discussed in this article, this accumulation is located in the microstructure around cementite, seen in a turn of hard magnetization toward soft magnetization proven by Barkhausen noise measurements. This decay is caused by the plastic deformation of such domains. Distortions in the vicinity of a cementite first would lead to carbon supersaturation by diffusion processes and later to a plastic deformation of the carbides. In the end, the complete distorted region will release the accumulated energy by downsizing the microstructure toward WEC.

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Section: Wec Microstructurementioning

confidence: 97%

White Etching Crack Root Cause Investigations

Holweger

Wolf

Merk

et al. 2014

Tribology Transactions

114

View full text Add to dashboard Cite

show abstract

“…The hardness of WEA is increased in comparison with the surrounding material [1,2,5,17], which can lead to the formation of cracks during loading due the mechanical incompatibility. From other side, the shear stresses usually accompany the cracks while loading and it may initiate a recrystallisation process on the edge of the crack [18,19]. The WEA consist of fine equiaxed grains with size of 10-50 nm [20,21], which can be formed by a recrystallisation process [20].…”

Section: The Hypothesis On Electromagnetic Initiation Of the Wecmentioning

confidence: 99%

The Numerical Model of Electrothermal Deformations of Carbides in Bearing Steel as the Possible Cause of White Etching Cracks Initiation

et al. 2015

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Despite the ongoing debates on influence of hydrogen uptake and penetration in the steel, pulsed and extraordinary fatigue on white etching cracks (WEC) formation in bearing steel SAE52100, the present paper proposes an alternative hypothesis on electrothermal initiation of the WEC. The hypothesis points to differences between electrical and thermal properties of elements of steel microstructure that lead sequentially to redistribution of current, resistivity heating, thermal expansion and deformations of the carbide particle. Appearance of a nano-void is also predicted by the model in the cases of the martensite and the bainite structures. The model also predicts higher probability of the WEC formation for the bainitic steel.

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“…One popular hypothesis is due to crack face rubbing causing a localised mechanical deformation during RCF (this being enhanced in the presence of diffusible hydrogen [36], higher concentrations could exist at these sites [37]), an associated material transfer from one side of the crack to the other occurs, and recrystallisation results [13,37,38]. A more recent hypothesis developed through modelling is energy dissipation at rubbing crack faces [35].…”

Section: Introductionmentioning

confidence: 99%

“…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%

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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Application of Complementary Techniques for Advanced Characterization of White Etching Cracks

Cited by 30 publications

References 11 publications

White Etching Crack Root Cause Investigations

White Etching Crack Root Cause Investigations

The Numerical Model of Electrothermal Deformations of Carbides in Bearing Steel as the Possible Cause of White Etching Cracks Initiation

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

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