Micro-Pitting and Wear Assessment of PAO vs Mineral-Based Engine Oil Operating under Mixed Lubrication Conditions: Effects of Lambda, Roughness Lay and Sliding Direction

Vrček, Aleks; Hultqvist, Tobias; Baubet, Yannick; Björling, Marcus; Marklund, Pär; Larsson, Roland

doi:10.3390/lubricants7050042

Cited by 16 publications

(8 citation statements)

References 28 publications

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“…28,29 Interesting to note is that the surface fatigue occurred regardless of high or mild wear taking place on the smoother surface (Test 17/18). Previous researches 16,17 showed that the same engine oil under similar operating conditions completely retards micro-pitting or surface fatigue damage by increasing the wear component. However, the surface roughness of the rough surface was slightly lower (RMS ¼ 300 nm) and both surfaces were harder ($66 HRC) in those studies.…”

Section: Surface Damage Characterizationmentioning

confidence: 98%

“…This in combination with elevated friction can promote micro-pitting damage. [11][12][13][14][15][16][17] However, under high loads and temperatures the ZDDP additive can increase wear by changing the wear mechanism from plowing/seizure to delamination wear of the surface layer, i.e. tribolayer.…”

Section: Introductionmentioning

confidence: 99%

“…It was demonstrated that the engine oil containing a reduced additive package allowed sufficient running-in wear to take place and significantly reduced the tendency towards micro-pitting. Furthermore, another study 17 showed that surface fatigue can be completely eliminated if the surface roughness lay is longitudinal in regards to the rolling direction, even in instances of elevated surface roughness. Additionally, micropitting damage can be eliminated if the hardness difference is sufficiently high between both surfaces in contact if the smoother surface is harder.…”

Section: Introductionmentioning

confidence: 99%

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Tribological characterization of potential crankshaft bearing steels for roller bearing engines

Vrček

Hultqvist

Jøhannesson

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part J:

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A crankshaft roller bearing internal combustion engine (ICE) offers a five percent or more improvement in overall engine efficiency and, thereby, a reduction in a five percent of CO2 emissions, compared to a plain bearing supported crankshaft. Current forged crankshaft steels represent the limiting factor of the rolling component, therefore, a replacement of the crankshaft steel is required. Apart from this, the tribology of the rolling contacts has been shown to be detrimental when lubricated with current engine oils. Therefore, this paper investigates the tribological performance of potential crankshaft bearing steels, i.e. DIN C56E2 (G55); DIN 50CrMo4 (G50); and DIN 100Cr6 (G3), while utilizing a state-of-the-art low viscosity 0W20 engine oil and under conditions prevalent to ICE. For this, damage mode investigation was performed in a disc-on-disc setup. Based on the results, wear damage of DIN 100Cr6 discs was shown to be dependent on the steel grade of which the counterpart disc was made from and surface hardness difference between both discs. In addition, surface fatigue and wear damage can be completely eliminated by selecting a proper surface roughness and hardness combination. Also, while under an elevated roughness level, engine oil was shown to promote both surface fatigue and wear damage through the work of ZDDP additives, which under extreme conditions can act as an extreme pressure (EP) additive. The residual stress measurements using the XRD technique revealed relatively high compressive residual stresses for G55 and G50 in comparison to G3 steel after surface induction hardening. In addition, no significant changes in residual stress for G55 and G50 were observed after the test. In contrast, relatively high tensile stress was observed for G3 near the surface region. This suggests that the most commonly used 100Cr6 bearing steel, in this case, is the most susceptible to surface fatigue.

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Section: Surface Damage Characterizationmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tribological characterization of potential crankshaft bearing steels for roller bearing engines

Vrček

Hultqvist

Jøhannesson

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…Vrcek et al [15] also showed that micropitting and wear damage are highly case-dependent. It can be found that PAO-based engine oil tends to eliminate micropitting damage compared to mineral-based engine oil under less severe lubricating conditions.…”

Section: State Of the Artmentioning

confidence: 99%

Eignung der Ergebnisse des Graufleckentests nach FVA 54/7 für moderne Getriebeanwendungen

Sagraloff

Tobie

Stahl

2021

Forsch Ingenieurwes

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A high load carrying capacity regarding micropitting is requested in many modern gear applications.The lubricant used has a great influence on the micropitting resistance of a gear-lubricant-system. As a result, it is highly recommended that a lubricant with a sufficient micropitting load-carrying capacity be used to avoid micropitting. Lubricants usually contain additives, which also have a strong effect on micropitting load-carrying capacity depending on operating temperature. As a result, the load-carrying capacity of gear lubricants cannot be determined theoretically and has to be determined by physical testing.A well-established test procedure to determine load-carrying capacity with regard to micropitting is the FVA/FZG-micropitting test according to FVA 54/7, which is also the basis of the recently published standard DIN 3990-16. This test method was defined about 30 years ago with standardized test gears, which differ from gears commonly used in modern applications. Therefore, the practicability of the test method needs to be reviewed and the suitability of the test results for modern practical gear applications needs to be verified.For this purpose, screening tests were conducted with case-hardened gears of materials 16MnCr5 and 18CrNiMo7‑6 to investigate the influence of the material on the results of the micropitting test. Additionally, the influence of test gears designed under consideration of practical applications on the test results was comprehensively examined. For this purpose, the micro-geometry (flank modifications), macro-geometry (helical gears) and grinding method (profile grinding) were altered.The results show that the results of the micropitting test according to FVA 54/7 with standard test gears made of 16MnCr5 can be applied to gears with the material, micro- and macro-geometry as well as grinding methods used commonly in practical applications. This paper presents and summarizes the results of these experimental investigations.

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“…Micro-pitting is a common failure mode in numerous tribological components including but not limited to gears, rolling bearings, and the surfaces of cams and tappets. Multiple factors in uence the surface contact fatigue phenomena involved including speci c lm thickness [4][5], contact pressure [6], slide-to-roll ratio [7][8],…”

Section: Introductionmentioning

confidence: 99%

Inhibition of Micro-pitting by Tribofilm-Forming ZrO2 Nanocrystal Lubricant Additives: A Micro-pitting Rig and Transmission Electron Microscope Study

et al. 2022

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The drive to reduce fuel consumption in transportation has encouraged the emergence of low viscosity lubricants to reduce viscous losses in the engine, drivetrain, and other components. However, viscosity reduction increases the risk of surface damage, thus motivating the development of new anti-wear (AW) additives. Capped ZrO2 nanocrystals (NCs) in base oils have been shown to form AW tribo lms within microscale sliding contacts. However, the potential of ZrO2 NCs to protect surfaces subjected to rollingsliding contact from macroscale damage, such as micro-pitting, remains unexplored. Here, we explore the ability of ZrO 2 NCs to form protective tribo lms under harsh conditions using a micro-pitting rig (MPR), consisting of a three ring-on-roller con guration. The experiments were conducted in polyalphaolephin (PAO) base oil, with and without 5 nm diameter ZrO2 NCs, at two levels of slide-to-roll ratio (SRR) (30% and 0%) and at variable test durations up to long durations (119 hours). MPR results showed the use of ZrO 2 NCs gives rise to the formation of a tribo lm covering the roller surfaces and decreases the initiation and propagation of micro-pits compared to tests in pure PAO base stock. Transmission electron microscopy (TEM) performed on focused ion beam (FIB) milled cross-sectional samples of the roller surfaces revealed the growth of dense and 50-100 nm thick ZrO 2 -based tribo lms independent of (SRR), indicating the potential for robust micro-pitting fatigue protection. Nevertheless, small cracks localized within the near surface region of the roller tested at the most severe conditions (30% SRR and 119 hours) were observed. The initiation of these cracks was directly related to the presence of manganese sulphide (MnS) inclusions in the steel, revealed using TEM combined with energy dispersive spectroscopy (EDS).The results highlight the bene ts of the protective tribo lms formed by ZrO 2 NCs and suggest approaches for further optimizing their use.

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Micro-Pitting and Wear Assessment of PAO vs Mineral-Based Engine Oil Operating under Mixed Lubrication Conditions: Effects of Lambda, Roughness Lay and Sliding Direction

Cited by 16 publications

References 28 publications

Tribological characterization of potential crankshaft bearing steels for roller bearing engines

Tribological characterization of potential crankshaft bearing steels for roller bearing engines

Eignung der Ergebnisse des Graufleckentests nach FVA 54/7 für moderne Getriebeanwendungen

Inhibition of Micro-pitting by Tribofilm-Forming ZrO2 Nanocrystal Lubricant Additives: A Micro-pitting Rig and Transmission Electron Microscope Study

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