The reaction layer formed on steel by additives based on sulphur and phosphorus compounds under conditions of boundary lubrication

Sakamoto, Tohru; Uetz, H.; Föhl, J.; Khosrawi, M.A.

doi:10.1016/0043-1648(82)90099-0

Cited by 21 publications

(6 citation statements)

References 19 publications

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“…This suggests that XPS data is influenced by the averaging effect over the analysed area. In addition, XPS depth profiling could not detect a distinct layer on the interface implying a localised formation of the iron sulphide near the micropit verifying previous studies[6,48] which suggest localised enrichment of sulfur traces around the pits.…”

supporting

confidence: 84%

Experimental observation of zinc dialkyl dithiophosphate (ZDDP)-induced iron sulphide formation

Soltanahmadi

Morina

Eijk

et al. 2017

Applied Surface Science

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Zinc Dialkyl DithioPhosphate (ZDDP) as a well-known anti-wear additive enhances the performance of the lubricant beyond its wear-protection action, through its anti-oxidant and Extreme Pressure (EP) functionality. In spite of over thirty years of research attempting to reveal the mechanism of action of ZDDP, there are still some uncertainties around the exact mechanisms of its action. This is especially the case with the role of sulphide layer formed in the tribofilm and its impact on surface fatigue. Although iron sulphide on the substrate is hypothesised in literature to form as a separate layer, there has been no concrete experimental observation on the distribution of the iron sulphide as a dispersed precipitate, distinct layer at the steel substrate or both. It remains to be clarified whether the iron sulphide layer homogeneously covers the surface or locally forms at the surface. In the current study a cross section of the specimen after experiment was prepared and has been investigated with Transmission Electron Microscopy (TEM) and Energy-Dispersive X-ray (EDX) elemental analysis. A 5-10 nm iron sulphide layer is visualised on the interface as a separate layer underneath the phosphate layer with an altered distribution of tribofilm elements near the crack site. The iron sulphide interface layer is more visible near the crack site where the concentration of the sulphur is enhanced. Also, ZDDP elements were clearly detected inside the crack with a varied relative concentration from the crack-mouth to the crack-tip. Sulphur is present inside the crack to a higher extent than in the bulk of the tribofilm.

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supporting

confidence: 84%

Experimental observation of zinc dialkyl dithiophosphate (ZDDP)-induced iron sulphide formation

Soltanahmadi

Morina

Eijk

et al. 2017

Applied Surface Science

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“…The centroids of the oxide features, 710.4 eV for Fe and 576.6 eV for Cr, correspond closely to binding energies expected for Fe 2 O 3 and Cr 2 0 3 , respectively. 12 .1 4 Starting from the bottom spectra of Figure 1, the sample was rotated toward the analyzer in 200 increments, increasing the effective electron escape depth, thus allowing greater contributions from bulk speces. The metallic peaks of both Fe and Cr become larger, relative to the oxide features, as the electron take-off angle increases from 300 at the bottom to 900 at the top of the figure.…”

Section: Results and Analysismentioning

confidence: 99%

Chemistry of the extreme-pressure lubricant additive lead naphthenate on steel surfaces

Didziulis¹,

Fleischauer²

1991

Langmuir

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The adsorption and chemical reactivity of the extreme-pressure (EP) oil additive lead naphthenate (Pbnp) on steel surfaces are examined with X-ray photoelectron spectroscopy. In addition, the chemical compositions of AISI 440C and 52100 steel surfaces are studied as a function of sample cleaning treatment, including solvent cleaning, and treatments with acidic and basic solutions. At room temperature, Pbnp is shown to physisorb on the iron oxide overlayer present on both steel surfaces following solvent cleaning. A chemisorbed form of Pbnp is characterized by Pb 4f peaks chemically shifted by 0.3-0.4 eV to lower binding energy and significantly lower intensity of the C Is feature associated with the Pbnp carboxylate group. This form of Pbnp is observed on acid-and base-pretreated surfaces that lose their iron oxide overlayers. The chemisorbed Pbnp surface species is also observed when the steel surfaces are scratched while being immersed in the Pbnp solution. When the Pbnp treated steel surfaces are heated to simulate the EP conditions for which Pbnp is used, most of the Pbnp on the oxide-covered surfaces desorbs. In addition, metallic Pb is readily formed on the scratched surfaces and on surfaces with significant amounts of metallic Fe. These results point to two possible modes of boundary protection: chemisorbed Pbnp under mild wear conditions and a layer of metallic Pb under severe wear conditions.

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“…Tests on AISI 52100 showed phosphorus enhanced films forming first on fresh surfaces, then sulphur enhanced films forming under increased loads and temperatures to prevent metal-metal contact. 158 However, chemically active EP additives, e.g. sulphur-phosphorous, can be detrimental to RCF life, 159 accelerating the progress of surface fatigue microcrack propagation when inside fissures in contact with a fresh steel surface, 160 and antiwear additives can produce an increase in friction and reduction in oil film thickness.…”

Section: Tribochemistry Lubrication and Additivesmentioning

confidence: 99%

White structure flaking (WSF) in wind turbine gearbox bearings: Effects of ‘butterflies’ and white etching cracks (WECs)

Evans

2012

Materials Science and Technology

220

214

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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) by the formation of butterflies and white etching cracks with associated microstructural change called white etching areas. Despite these failures having been observed for two decades in various industries, the detailed reasons and mechanisms for their formation are not fully understood. In this review, white etching area formation mechanisms are discussed, specifically grain refinement, and effects of carbon/carbide in a range of bearing steels of widely differing carbon content. The review also highlights the severe transient, cyclic loading and tribochemical operating conditions of gearbox bearings and explains how these may act as drivers to produce WSF. Much previous research has focused on the detrimental effects of hydrogen, but other work suggests that hydrogen is not the only cause for WSF. Possible methods for preventing WSF are discussed, with attention paid to special steels such as high chromium steels, low carbon stainless nitrogen alloy steels and carbonitrided steels. Beneficial compressive residual stresses, surface coatings and enhanced lubrication and additive packages are shown to offer degrees of prevention, although the mechanisms leading to improvements are not fully understood.

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The reaction layer formed on steel by additives based on sulphur and phosphorus compounds under conditions of boundary lubrication

Cited by 21 publications

References 19 publications

Experimental observation of zinc dialkyl dithiophosphate (ZDDP)-induced iron sulphide formation

Experimental observation of zinc dialkyl dithiophosphate (ZDDP)-induced iron sulphide formation

Chemistry of the extreme-pressure lubricant additive lead naphthenate on steel surfaces

White structure flaking (WSF) in wind turbine gearbox bearings: Effects of ‘butterflies’ and white etching cracks (WECs)

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