Effect of lubricant additives in rolling contact fatigue

Experimental investigations were carried out to better understand the rolling contact fatigue mechanisms in nitrided layers of the 33CrMoV12-9 steel grade. Surface-initiated pitting failure mode was reproduced on a twin-disc machine to analyse crack growth and compressive residual stress behaviour within the nitrided layers. Metallographic examinations, 3D observations by means of high-resolution X-ray computed tomography and residual stress analysis were realised on nitrided 33CrMoV12-9 specimens before and after rolling contact fatigue tests. The study revealed that if the initial compressive residual stresses associated with the surface treatment are released during the process of rolling contact fatigue, pre-existing superficial cracks propagate in the nitrided layers along the intergranular carbides. These precipitates induced by the nitriding process therefore act as preferential crack propagation sites.

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“…2. Environmental parameters such as lubrication, 3,4 hydrogen embrittlement, 5 etc. influence the crack mechanisms 3.…”

Section: Introductionmentioning

confidence: 99%

Rolling contact fatigue crack propagation in nitrided alloyed steels

Ville

Kléber

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…The additives used in the oils in this study resulted in thin tribofilms, and it is unlikely that they will offer any significant mechanical support to initiated cracks as suggested in Meheux, et al (26). They are also unlikely to enhance pitting life by separating the surfaces or reduce the severity of asperity interactions as reported in the work of Fowles, et al (27).…”

Section: Hypothesismentioning

confidence: 66%

Improving Hypoid Gear Oil Pitting Performance through Friction Reduction

Johansson

Devlin²,

Guevremont³

et al. 2019

Tribology Transactions

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Earlier studies have shown that the load-dependent friction behavior of various gear oils can affect their pitting performance; that is, low friction resulted in a long pitting life. These studies were limited, however, to test methods and running conditions quite different from those occurring in actual gear transmissions. In the present study, a more gear-like twin-disc machine with test specimens and running conditions relevant for gear contacts was used to investigate whether the same trends could be found. To analyze this possible correlation, the first step was to prepare a set of hypoid gear oils and to test their friction performance to compare various ways of improving friction behavior but also to form an understanding of why their friction performance varied. The second step was to test the pitting performance of the oils. The pitting results could then be compared to the friction properties of the oils to analyze the correlation. Other possible mechanisms behind the formation of pits are also discussed. The results show that for the oils included, the antiwear and extreme-pressure additive package and the base oil type affect friction. The results further show that additive combinations and/or base oils that result in low friction lead to enhanced pitting performance.

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“…A number of additives found in lubricants have been shown to promote WSF occurrence, these include; extreme pressure (EP) and anti-wear (AW) additives consisting of sulphur and phosphorus compounds [66,67], where sulphur aids in hydrogen diffusion by preventing atomic hydrogen recombination [68] and formulations of AW zinc dithiophosphates (ZDDP/ZnDTP/ZnDDP) with detergent/rust preventative calcium sulphonate additives [6,61,[69][70][71][72][73][74].…”

Section: Influence Of Oilmentioning

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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Effect of lubricant additives in rolling contact fatigue

Cited by 18 publications

References 21 publications

Rolling contact fatigue crack propagation in nitrided alloyed steels

Rolling contact fatigue crack propagation in nitrided alloyed steels

Improving Hypoid Gear Oil Pitting Performance through Friction Reduction

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

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