Surface Chemistry of Chlorinated Hydrocarbon Lubricant Additives–-Part II: Modeling the Tribological Interface

Blunt, T. J.; Kotvis, Peter V.; Tysoe, Wilfred T.

doi:10.1080/10402009808983731

Cited by 26 publications

(12 citation statements)

References 11 publications

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“…That is, the tribopin was either slid over a new region of the KCl-covered iron without heating the tribopin (Trace A) or heated and slid over the same region (Trace B). In contrast to the behavior seen for FeCl 2 (Fig. 7), only slight differences are found in the resulting friction coefficient.…”

Section: Resultscontrasting

confidence: 44%

“…The corresponding comparison of contact resistances are displayed in Fig. 9 for the first () and second (᭹) passes where a similar phenomenon is found as for FeCl 2 (Fig. 2) where the contact resistance is lower in the second pass than the first.…”

Section: Resultsmentioning

confidence: 70%

“…In the experiments carried out here with a tungsten carbide ball and clean iron substrates, it has been shown that the iron substrate is much smoother than the tungsten carbide ball [6], which shows an approximately Gaussian height distribution with a width of ∼2000 Å. Some penetration of the film is noted from the contact resistance measurements for FeCl 2 (Fig. 2), which does not reach its limiting value until 500 Å of FeCl 2 has been deposited.…”

Section: Discussionmentioning

confidence: 93%

“…As noted above, these materials have completely different crystal structures, where KCl adopts the cubic sodium-chloride-like structure, while ferrous chloride has a layered rhombohedral CdCl 2 structure (space group R3m) [8]. The frictional properties of KCl have been studied previously [6,13] and FeCl 2 is the predominant component of tribological films formed when using chlorinated hydrocarbon extreme-pressure additives [1,2,[16][17][18][19][20]. Experiments are carried out in ultrahigh vacuum using a pin-on-disk configuration using a ball (tungsten carbide) of radius 6.35 × 10 −3 m, where the load varies between 0.29 and 1.2 N, corresponding to maximum Hertzian pressures of ∼420-670 MPa, respectively [21].…”

Section: Introductionmentioning

confidence: 99%

“…We have shown previously that an extreme-pressure film consisting primarily of FeCl 2 is formed reactively when using model extreme-pressure lubricants consisting of methylene chloride, chloroform or carbon tetrachloride dissolved in a poly ␣-olefin [1,2]. These experiments were performed in a pin and v-block apparatus where friction coefficients were found to be (11 ± 1) × 10 −2 (for a film formed from methylene chloride [3]) and (7.1 ± 0.2) × 10 −2 (for a film from chloroform or carbon tetrachloride [4,5]).…”

Section: Introductionmentioning

confidence: 99%

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The friction, mobility and transfer of tribological films: potassium chloride and ferrous chloride on iron

Gao

Kotvis

2004

Wear

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The tribological properties of FeCl 2 , measured using an ultrahigh vacuum tribometer, are compared with those of KCl. The friction coefficient of an FeCl 2 film evaporated onto iron in ultrahigh vacuum decreases to ∼0.08 after the deposition of a film ∼40 Å thick. This value is in good agreement with that measured for reactively formed FeCl 2 films in a pin and v-block apparatus. The contact resistance also increases at the same FeCl 2 thickness as that at which the friction coefficient reaches its minimum value suggesting that this corresponds to the completion of the first monolayer as found previously for KCl. Comparison of the friction coefficients and contact resistances for a second pass suggests that the film is mobile during rubbing in both cases. It is found that repeated rubbing in the case of FeCl 2 leads to a reduction in friction coefficient to ∼0.015 which is shown to be due to the formation of a transfer film on the tribotip. In contrast, no such reduction is found for a KCl film up to 40 cycles, implying that no transfer film is formed in that case. It is also found that, while friction reduction requires the surface to be completely covered by the halide film, suppression of damage in the iron requires the deposition of films thicker than ∼500 Å.

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Section: Resultscontrasting

confidence: 44%

Section: Resultsmentioning

confidence: 70%

Section: Discussionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The friction, mobility and transfer of tribological films: potassium chloride and ferrous chloride on iron

Gao

Kotvis

2004

Wear

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Reaction of tributyl phosphate with oxidized iron: surface chemistry and tribological significance

et al. 2005

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The chemistry of tributyl phosphate on Fe 3 O 4 was studied in ultrahigh vacuum using temperature-programmed desorption (TPD) and Auger spectroscopy. A portion of the tributyl phosphate desorbs intact with an activation energy of $120 kJ/mol. The remainder decomposes either by PAO bond scission to deposit surface butoxy species or appears to dehydrogenate desorbing C 2 or C 3 compounds and depositing hydrogen and carbon on the surface. The resulting hydrogen reacts either with the oxide to desorb water or with butoxy species yielding 1-butanol. The remaining butoxy species are stable up to $600 K where they decompose to desorb butanal via hydride elimination where again the hydrogen reacts with butoxy species to form 1-butanol or with the oxide to form water. The carbon deposited onto the surface further reduces the oxide to desorb as CO above $750 K, although a small amount of carbon is detected on the surface using Auger spectroscopy. Substantially larger amounts of carbon are deposited onto the surface when Fe 3 O 4 is exposed to tributyl phosphate at 300 K, where an Auger depth profile reveals that the carbon is located at the surface while the PO x species formed by tributyl phosphate decomposition diffuse rapidly into the oxide layer, leading to a film structure in which graphitic carbon is deposited onto a phosphorus-containing oxide layer.

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Tribological Properties of Films Formed by the Reaction of Carbon Tetrachloride with Iron

2005

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The tribological properties of halide films grown on iron by reaction with carbon tetrachloride vapor at a temperature of 617 K and a pressure of 1.7 Torr are compared, in ultrahigh vacuum, with FeCl 2 films evaporated onto the surface. It is found that the reactively formed film has a slightly lower limiting friction coefficient than the evaporated layer ($0.06 compared to $0.08), which may be due either to the diffusion of some carbon into the substrate or the formation of a more oriented layer when this is formed reactively. The major difference between the reactively grown and evaporated film is that the evaporated layer attains the minimum friction when $40 Å of FeCl 2 has been evaporated, while the reactively formed layer has a minimum friction coefficient when a film of 6±2 Å has been deposited. In the case of the evaporated FeCl 2 film, the growth of second and subsequent layers proceeds before the first layer is complete. It has been shown that the friction coefficient reaches its minimum value after completion of the first monolayer, a process that is complete after the evaporation of $40 Å of FeCl 2 . In the case of the film formed by reaction with CCl 4 , the halide film grows directly on the surface implying that the FeCl 2 monolayer thickness is $6 Å . This value is in good agreement with the layer thickness in bulk ferrous chloride.

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Surface Chemistry of Chlorinated Hydrocarbon Lubricant Additives–-Part II: Modeling the Tribological Interface

Cited by 26 publications

References 11 publications

The friction, mobility and transfer of tribological films: potassium chloride and ferrous chloride on iron

The friction, mobility and transfer of tribological films: potassium chloride and ferrous chloride on iron

Reaction of tributyl phosphate with oxidized iron: surface chemistry and tribological significance

Tribological Properties of Films Formed by the Reaction of Carbon Tetrachloride with Iron

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