Morphological evolution of films formed from thermooxidative decomposition of ZDDP

Aktary, Mirwais; McDermott, Mark T.; Torkelson, Jeff R.

doi:10.1016/s0043-1648(00)00525-1

Cited by 45 publications

(32 citation statements)

References 14 publications

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“…Using oil B, Figure 12e and 12f show the SEM image of the tribofilm formed on the surface of the polished insert. Continuous padlike layers that are separated by craters were observed on the insert surface although this was more conspicuous at 105 0 C. This has been reported for model oils containing ZDDP [46]. The films appear significantly thicker and more evenly distributed on the surface than oil A.…”

Section: Scanning Electron Microscopy/energy Dispersive X-rays (Sem/edx)supporting

confidence: 50%

Development of valve train rig for assessment of cam/follower tribochemistry

Ofune

Banks

Morina

et al. 2016

Tribology International

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Component bench tests are a crucial part of a tribology assessment experimental programme for most engines and subsystems. This is because they test the components under conditions simulating the operating characteristics of the system. These have become very important as they shed more light into the friction, wear, lubrication and importantly for this study, the tribochemistry of valve train systems. This work outlines the procedure for the development of a single cam rig (SCR) from a 1.25L FORD Zetec (SE) engine. Friction plots were used to validate the data obtained from the newly developed single cam rig with Mn-phosphate coated and polished follower against a cast iron camshaft. The tribofilm formed using normal and mid Sulphated Ash, Phosphorus and Sulphur (SAPS) 5W-30 oils were evaluated and correlated to the friction and wear properties of the tribopair.Raman and FIB-SEM/EDX investigations of the tribochemical films showed that the normal SAPS oil produced patchy, thick (80-100 nm) and well dispersed tribofilm with better wear prevention capabilities. It was observed that Mid SAPS oil had lower wear prevention due to loosely dispersed and thin tribofilms. Absence of tribofilms at the centre of the insert with this oil also suggests that formation and removal processes are an integral part of the wear mechanisms in highly loaded cam follower systems.

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Section: Scanning Electron Microscopy/energy Dispersive X-rays (Sem/edx)supporting

confidence: 50%

Development of valve train rig for assessment of cam/follower tribochemistry

Ofune

Banks

Morina

et al. 2016

Tribology International

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“…Overall, there is no consensus on the growth mechanism, and no models conclusively explain either the tribofilm patchiness or why the film thickness is limited. All prior experiments have been conducted for macroscopic, multi-asperity contacts (specific asperity contact areas and pressures thus being unknown) that are then analyzed post mortem and ex situ, often after extracting the sample from base stock, potentially altering the tribofilm (20) formed from adsorbed decomposition products of ZDDP (15,24). Typical thermal film thicknesses of ~10 nm were obtained after ~1 hour of heating the base stock bath, but can increase with time (24).…”

Section: Main Textmentioning

confidence: 99%

“…All prior experiments have been conducted for macroscopic, multi-asperity contacts (specific asperity contact areas and pressures thus being unknown) that are then analyzed post mortem and ex situ, often after extracting the sample from base stock, potentially altering the tribofilm (20) formed from adsorbed decomposition products of ZDDP (15,24). Typical thermal film thicknesses of ~10 nm were obtained after ~1 hour of heating the base stock bath, but can increase with time (24). After removing the thermal film with the tip, sliding is continued within the same region with a higher normal load to induce the growth of the tribofilm.…”

Section: Main Textmentioning

confidence: 99%

Mechanisms of antiwear tribofilm growth revealed in situ by single-asperity sliding contacts

Gosvami

Bares

Mangolini

et al. 2015

Science

455

460

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Zinc dialkyldithiophosphates (ZDDPs) form antiwear tribofilms at sliding interfaces and are widely used as additives in automotive lubricants. The mechanisms governing the tribofilm growth are not well understood, which limits the development of replacements that offer better performance and are less likely to degrade automobile catalytic converters over time. Using atomic force microscopy in ZDDP-containing lubricant base stock at elevated temperatures, we monitored the growth and properties of the tribofilms in situ in well-defined single-asperity sliding nanocontacts. Surface-based nucleation, growth, and thickness saturation of patchy tribofilms were observed. The growth rate increased exponentially with either applied compressive stress or temperature, consistent with a thermally activated, stress-assisted reaction rate model. Although some models rely on the presence of iron to catalyze tribofilm growth, the films grew regardless of the presence of iron on either the tip or substrate, highlighting the critical role of stress and thermal activation.

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“…ZDDP usually decomposes on the ferrous surfaces and then it reacts with Fe 2 O 3 from either wear debris/ ferrous surface and form strongly bonded Zn-phosphate anti-wear compounds [55][56][57].…”

Section: Lubrication Comparison Of A-c:15h/ci and Steel/cimentioning

confidence: 99%

Tribological performance and tribochemical processes in a DLC/steel system when lubricated in a fully formulated oil and base oil

Kosarieh

Morina

Lainé

et al. 2013

Surface and Coatings Technology

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Abstract:Diamond-like carbon (DLC) coatings show extremely good promise for a number of applications in automotive components as they exhibit excellent tribological properties such as low friction and good wear resistance. This can impact on improved fuel economy and durability of the engine components. Much work has been reported on the dry sliding of DLC coatings with less so in lubricated contacts and, as such, there is a need to further understand the tribochemistry of lubricated DLC contacts. Commercially-available oils are normally optimized to work on ferrous surfaces. Previous studies on DLC lubricated contacts have tended to use model oil systems rather than fully formulated lubricants and from this an interesting picture of lubrication mechanisms is emerging. Optimising compatibility between a surface and a set of lubricant additives may lead to excellent durability (wear) as well as increased fuel economy (low friction). In this work, the friction and wear properties of a DLC coating under boundary lubrication conditions have been investigated and the tribological performance compared with that of an uncoated steel system. A pin-on-plate tribotester was used to run the experiments using High speed steel (HSS) M2 grade plates coated with 15 at.% hydrogenated DLC (a-C:15H) sliding against cast iron pins. A Group III mineral base oil, fully synthetic Group IV PAO and four different fully formulated oils were used in this study. Furthermore optical and scanning electron microscopes (SEM) were used to observe the wear scar and to assess the durability of the coatings. Energy-Dispersive X-ray analysis (EDX), X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy analyses were performed on the tribofilms to understand the tribochemical interactions between oil additives and the a-C:15H coating.This study show that the durability of the a-C:15H coating strongly depends on the selected additive package in the oils. In addition the effect of detergent, dispersant and antioxidants on the performance of the Molybdenum-based friction modifier (Mo-FM) and ZDDP anti-wear additive were investigated and results are reported in this paper.

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Morphological evolution of films formed from thermooxidative decomposition of ZDDP

Cited by 45 publications

References 14 publications

Development of valve train rig for assessment of cam/follower tribochemistry

Development of valve train rig for assessment of cam/follower tribochemistry

Mechanisms of antiwear tribofilm growth revealed in situ by single-asperity sliding contacts

Tribological performance and tribochemical processes in a DLC/steel system when lubricated in a fully formulated oil and base oil

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