Steels for bearings

Ball and rolling element bearings are perhaps the most widely used components in industrial machinery. They are used to support load and allow relative motion inherent in the mechanism to take place. Subsurface originated spalling has been recognized as one of the main modes of failure for rolling contact fatigue (RCF) of bearings. In the past few decades a significant number of investigators have attempted to determine the physical mechanisms involved in rolling contact fatigue of bearings and proposed models to predict their fatigue lives. In this paper, some of the most widely used RCF models are reviewed and discussed, and their limitations are addressed. The paper also presents the modeling approaches recently proposed by the authors to develop life models and better understanding of the RCF.

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A Review of Rolling Contact Fatigue

Rolling contact failures are classified according to their failure mode as (a) wear, (b) plastic flow, (c) fatigue, and (d) bulk failures, with the last class arising outside the immediate contact area. The wear failures are subdivided into mild wear by loose particle removal and smearing involving metal transfer. Plastic failures may arise due to overload or to temperature imbalance. Fatigue is of the spalling or the surface distress type. An analysis of the stress conditions in a rolling contact is sketched; the stepwise refinements of the contact model are considered, starting from Hertz theory, and progressively including surface traction, plasticity, elastohydrodynamic lubricant films, surface microtopography, and the inhomogeneities of real metals, Each failure mode is associated with the relevant severity parameters of the contact stress condition, and a description of its mode of formation is given. Guidelines are provided for the identification of that failure mode which, among competing modes, i...

On Competing Failure Modes in Rolling Contact

The actual service life of wind turbine gearboxes is often well below the desired 20 years. One of the prevalent failure modes in gearbox bearing raceways is white structure flaking (WSF) in as little as 6–24 months of operation by the formation of axial cracks and white etching cracks (WECs) with associated microstructural change called white etching areas (WEAs). Despite these failures having been observed for two decades in various industries, the drivers and mechanisms for their formation are still highly contested. Discussed in this review are methods for searching and analysing WECs, mechanisms for WEA microstructural change, WEC initiation and propagation theories, WSF formation drivers and finally technologies and processes offering resistance to WSF. This updated review serves as a recap, comprehensive update on findings, current focus areas and remaining challenges.This paper is part of a Themed Issue on Recent developments in bearing steels.

An updated review: white etching cracks (WECs) and axial cracks in wind turbine gearbox bearings

Elastohydrodynamic (EHD) film thickness measurements using optical interferometry have been made of artificially produced dents and grooves under rolling and sliding conditions. These measurements are compared to stylus traces of the dent and groove profiles to determine the local deformation associated with micro-EHD pressure generation. The surface geometry associated with the dents and grooves is seen to become intimately involved in the lubrication process itself, creating local pressure variations that substantially deform the local surface geometry, particularly under sliding conditions. The rolling results have implications concerning surface initiated fatigue and the sliding results show clearly the EHD surface interactions that must occur prior to scuffing failure. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Minneapolis, Minnesota, October 24–26, 1978

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Elastohydrodynamic Film Thickness Measurements of Artificially Produced Surface Dents and Grooves

Rolling induced residual stress measurements as function of depth and component Rockwell hardness for inner races from deep groove ball bearings

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A Study of Residual Stress Induced During Rolling

Component hardness differences of SAE 52100 steel effect on bearing fatigue, using five-ball fatigue tester and rolling element bearings

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Component Hardness Differences and Their Effect on Bearing Fatigue

The NASA five-ball fatigue tester was used to determine the rolling-contact fatigue life of ½-in.-diameter M-1 steel balls applicable for high-temperature bearing use, and modified 204-size angular-contact ball bearings at various contact angles. For a constant Contact stress in the five-ball fatigue tester, fatigue life decreased with increasing contact angle. In contrast, relative thrust-load capacity increased with increasing contact angle. The Lundberg-Palmgren theory correctly predicts capacity at contact angles up to 30 degrees. Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Chicago, Illinois, October 1961.

The Effect of Contact Angle on Rolling-Contact Fatigue and Bearing Load Capacity

Hot-pressed silicon nitride was evaluated as a rolling-element bearing material. The five-ball fatigue tester was used to test 12.7-mm- diameter silicon nitride balls at maximum Hertz stresses ranging from 4.27 x 10 to the 9th power n/sq m to 6.21 x 10 to the 9th power n/sq m at a race temperature of 328K. The fatigue life of NC-132 hot-pressed silicon nitride was found to be equal to typical bearing steels and much greater than other ceramic or cermet materials at the same stress levels. A digital computer program was used to predict the fatigue life of 120-mm- bore angular-contact ball bearings containing either steel or silicon nitride balls. The analysis indicates that there is no improvement in the lives of bearings of the same geometry operating at DN values from 2 to 4 million where silicon nitride balls are used in place of steel balls.

Fatigue life of high-speed ball bearings with silicon nitride balls

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Richard J. Parker

Papers

A Study of Residual Stress Induced During Rolling

Component Hardness Differences and Their Effect on Bearing Fatigue

The Effect of Contact Angle on Rolling-Contact Fatigue and Bearing Load Capacity

Fatigue life of high-speed ball bearings with silicon nitride balls

Fatigue Life of High-Speed Ball Bearings With Silicon Nitride Balls