Nanometer Scale Chemomechanical Characterization of Antiwear Films

Nicholls, Mark A.; Norton, P. R.; Bancroft, G.M.; Kasrai, M.; Do, T.; Frazer, B. H.; Stasió, Gelsomina De

doi:10.1023/b:tril.0000032447.32442.6a

Cited by 80 publications

(126 citation statements)

References 47 publications

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“…In addition XPS analysis results confirm that the top part of the tribofilm contains mainly longer chain polyphosphates than the bulk [13,16,17,24,52]. It can be interpreted that higher temperature can result in changes in the structure of the tribofilm thus changing the mechanical properties of the glassy phosphates.…”

Section: Chemistry Of the Tribofilmsupporting

confidence: 56%

“…The value of BO/NBO ratio was 0.51 (metaphosphate) in case of ZDDP replaced by fresh ZDDP (point C1 in Figure 5) and 0.62 (metaphosphate) when ZDDP changed with base oil and then replaced by fresh ZDDP again (C5 in Figure 9). It has also been shown in the literature that unreacted ZDDP can be replenished in the contact areas and reform glassy polyphosphates [16]. The difference in the values of binding energy (eV) between Zn3s and P2p was 6.4 (point C1 in Figure 5) and 6.32 (point C5 in Figure 9), respectively.…”

Section: Chemistry Of the Tribofilmmentioning

confidence: 75%

“…Several works have studied the mechanical properties of ZDDP tribofilms formed in boundary lubricated contacts [13][14][15][16][17][18][19]. These have demonstrated that the properties of the ZDDP tribofilm layers are dependent on applied load [20,21].…”

Section: Mechanical Properties and Durability Of Zddp Tribofilmmentioning

confidence: 99%

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A new insight into the interfacial mechanisms of the tribofilm formed by zinc dialkyl dithiophosphate

Parsaeian

Ghanbarzadeh

Eijk

et al. 2017

Applied Surface Science

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Understanding the true interfacial mechanisms involved in the growth of tribofilms generated by Zinc Dialkyl Dithiophosphate (ZDDP) is important because it is the most widely used antiwear additive and there is legislative pressure to find efficient environmentally-friendly replacements. The main focus of this study is to investigate the durability of the ZDDP tribofilm and correlate it to the chemical and physical properties of the glassy polyphosphates.A novel experimental method has been developed to study the effect of lubricant temperature and contact load on tribofilm growth and durability. Results show that physical parameters such as temperature and pressure significantly influence the tribofilm durability. XPS analyses were carried out before suspending the test and after changing the oil to assess the difference in chemical structure of the tribofilm before and after stopping the test. The chemical analyses suggest that there are different chemical properties across the thickness of the tribofilm and these determine the durability characteristics.

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Section: Chemistry Of the Tribofilmsupporting

confidence: 56%

Section: Chemistry Of the Tribofilmmentioning

confidence: 75%

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A new insight into the interfacial mechanisms of the tribofilm formed by zinc dialkyl dithiophosphate

Parsaeian

Ghanbarzadeh

Eijk

et al. 2017

Applied Surface Science

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“…For this reason, the development of new techinques for in situ tribological measurements is necessary to shed light into boundary lubrication wear mechanisms. Many previous publications on ZnDTP have hypothesized that the formation of mixed iron and zinc polyphosphate, as a consequence of the reaction of iron oxide with zinc polyphosphates, can promote the formation and adhesion of the polyphosphate tribofilm on the steel surface [3,32,33]. The quartz balls have been analyzed after the tribotests, in order to ascertain the ability of zinc polyphosphates to form adhesive transfer films on an inert material.…”

Section: Formation and Functionality Of The Transfer Filmmentioning

confidence: 99%

Effect of Chain-Length and Countersurface on the Tribochemistry of Bulk Zinc Polyphosphate Glasses

2012

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Zinc polyphosphate glasses are considered to be chiefly responsible for the anti-wear efficiency of ZnDTP tribofilms. In this work, the tribochemical properties of amorphous bulk zinc polyphosphates of different chain lengths (ranging from zinc metaphosphate to zinc pyrophosphate) have been investigated. Tribological tests on bulk polyphosphate discs have been carried out using steel and quartz balls as counter-surfaces in a poly-a-olefin (PAO) bath at room temperature. The composition in the wear track and on the contact region of the balls has been monitored by small-area and imaging X-ray photoelectron spectroscopy (i-XPS). The XPS analysis revealed that the composition of short-chain-length polyphosphates remained unchanged following tribological stress. Long-chain-length polyphosphates are depolymerized in the wear track as a consequence of a tribochemical reaction. By comparing the results obtained using quartz and steel balls, it could be observed that while the reaction of iron oxide with the polyphosphates certainly plays a role in the depolymerization of the samples under sliding conditions, pressure and shear stress alone and also in the presence of water or oil-oxidized species are able to depolymerize the glass when an inert material is used as counterpart; the composition of the wear track, in this case, is dependent on the applied load. All samples were able to form an adhesive, glassy transfer film on both steel and quartz balls, but the short-chain-length polyphosphates showed a lower friction coefficient and wear coefficient. The results suggest a third-body mechanism with the polyphosphates acting as a solid lubricant. Differences in tribological behavior of the different-chain-length polyphosphates are attributable to their mechanical and rheological properties.

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“…In addition, several other studies [26,36] examined the effect of detergents and dispersants on the decomposition reactions and the synergy between the different oil additives. Some of these XAS measurements were combined with X-ray photoelectron emission microscopy (X-PEEM) [27,31,37] and Photoelectron Emission Microscope by Synchrotron Undulator Illumination technique [38]. A review of the different contributions of these various XAS techniques to tribology was provided by Nicholls et al [27], which highlighted the importance of XAS especially in studying the reactions of oil additives and the composition of the formed tribofilms.…”

Section: Introductionmentioning

confidence: 99%

An in situ synchrotron XAS methodology for surface analysis under high temperature, pressure, and shear

Dorgham

Neville

Ignatyev

et al. 2017

Review of Scientific Instruments

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The complex tribochemical nature of lubricated tribological contacts is inaccessible in real time without altering their initial state. To overcome this issue, a new design of a pin-on-disc tribological apparatus was developed and combined with synchrotron X-ray absorption spectroscopy (XAS). Using the designed apparatus, it is possible to study in situ the transient decomposition reactions of various oil additives on different surfaces under a wide range of realistic operating conditions of contact pressure (1.0–3.0 GPa), temperature (25–120 °C), and sliding speed (30–3000 rpm or 0.15–15 m/s). To test the apparatus, several tribological tests were performed at different shearing times ranging from 2.5 to 60 min. These tests were carried out under helium atmosphere at a temperature of 80 °C, contact pressure of 2.2 GPa, and sliding speed of 50 rpm. The XAS experiments indicate that the zinc dialkyldithiophosphate antiwear additive decomposes in the oil to form a tribofilm on the iron surface at different reaction kinetics from the ones of the thermal film. The tribofilm composition evolves much faster than the one of the thermal film, which confirms that the formation of the tribofilm is a thermally activated process similar to the one of the thermal film but accelerated by shear. Furthermore, the results indicate that the sulfur of the formed film, whether a tribofilm or a thermal film, appears initially in the form of sulfate, with some sulfide, which under heat or shear is reduced into mainly sulfide.

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Nanometer Scale Chemomechanical Characterization of Antiwear Films

Cited by 80 publications

References 47 publications

A new insight into the interfacial mechanisms of the tribofilm formed by zinc dialkyl dithiophosphate

A new insight into the interfacial mechanisms of the tribofilm formed by zinc dialkyl dithiophosphate

Effect of Chain-Length and Countersurface on the Tribochemistry of Bulk Zinc Polyphosphate Glasses

An in situ synchrotron XAS methodology for surface analysis under high temperature, pressure, and shear

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