Effect of Surface Roughness on Tribochemical Decomposition of Synthetic Oils under High-Vacuum Conditions

Takiwatari, Koji; Nanao, Hidetaka; Hoshi, Yasushi; Uchidate, Michimasa; Mori, Shigeyuki

doi:10.2474/trol.14.398

Cited by 3 publications

(3 citation statements)

References 14 publications

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“…The decomposition of alkyl diphenyl ether was affected by the surface roughness of the disk specimen. 48 This result indicates that a nascent steel surface was readily formed on a rough surface.…”

Section: ■ Results and Discussionmentioning

confidence: 87%

“…Therefore, the tribochemical decomposition of MAC likely occurred through the synergistic effects of frictional heat and the active nascent surface, which was formed on sliding for more than 1 km, as shown in Figure . The decomposition of alkyl diphenyl ether was affected by the surface roughness of the disk specimen . This result indicates that a nascent steel surface was readily formed on a rough surface.…”

Section: Resultsmentioning

confidence: 97%

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Chemical Activity of Nascent Surfaces for Tribochemical Reactions of Lubricant Components

Mori,

Nanao,

Takiwatari

2024

Langmuir

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Boundary lubrication characteristics are strongly dependent on tribochemical reactions at the contact interface. There are multiple factors that contribute to the activity of tribochemical reactions and the complexity of this phenomenon. Here, we focused on nascent surfaces created by friction and aimed to clarify their chemical properties. To achieve this, we first developed a method based on a mass spectrometer that can sensitively detect molecular adsorption and reactions on a nascent surface. We used various organic compounds as adsorbates and friction materials such as steel, aluminum, gold, and ceramics and examined adsorption of the organic compounds on the nascent surfaces. The adsorption properties of the additives differed between steel metal oxide and nascent steel surfaces. For example, polar organic phosphates, which are extreme-pressure additives, were more easily adsorbed on oxide surfaces, whereas nonpolar organic sulfur compounds were more easily adsorbed on nascent steel surfaces. Alcohols and ethers also adsorbed on nascent aluminum surfaces, whereas olefins and benzene did not. Nascent gold surfaces showed high catalytic activity. Saturated hydrocarbons and fluorinated compounds, which are chemically inert, were also adsorbed on nascent ceramic surfaces, showing high activity. Hydrocarbon oils decomposed through the influence of frictional heat on a nascent steel surface to generate hydrogen and methane. We applied reactive molecular dynamics to simulate the adsorption phenomenon on iron surfaces. As a result, the adsorption energy obtained by simulation and the experimentally determined adsorption activity correlated well. Thus, adsorption and reaction behaviors on nascent surfaces inferred by our method were theoretically supported. On the basis of the chemical properties of the nascent surfaces obtained here, it is possible to explain boundary lubrication phenomena.

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Section: ■ Results and Discussionmentioning

confidence: 87%

Section: Resultsmentioning

confidence: 97%

Chemical Activity of Nascent Surfaces for Tribochemical Reactions of Lubricant Components

Mori,

Nanao,

Takiwatari

2024

Langmuir

Self Cite

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“…MAC oil was decomposed by the chemical effect of the nascent metal surface formed by mechanical removal of the surface oxide layer. The desorption rate of hydrogen was dependent on the lubrication conditions [8] and surface roughness of the specimens [9] and was suppressed by the lubricant additives [10].…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Evolution during Friction from Chemisorbed Water on Metals and Alloys

et al. 2022

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In this study, hydrogen formation was investigated during lubrication tests, which were carried out with synthetic hydrocarbon oil under high-vacuum conditions using disks made of Fe, Cr, SUS304, SUS440C, and SUJ2. The evolved gases were detected using a quadrupole mass spectrometer. Hydrogen evolution was observed at the beginning of the sliding. Hydrogen and hydrocarbons were formed simultaneously after 1 km of sliding distance. The hydrocarbon oil was decomposed tribochemically by the same point. When SUS304 was used as the specimen, a higher rate of hydrogen evolution was observed at the beginning of the sliding action compared to the other metals. X-ray photoelectron spectroscopy of the disk surface revealed that there was a thicker oxide film and large amount of chemisorbed water on SUS304. These results suggest that the chemisorbed water on SUS304 could be a source of hydrogen. When the SUS304 specimen was pretreated with heavy water, hydrogen deuteride ion was detected during the lubrication test. It can be concluded that chemisorbed water on metal surfaces is a source of tribochemically-formed hydrogen during lubrication tests. The sharp decrease in hydrogen evolution at the beginning of sliding is related to the destruction and removal of the oxide film.

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Hydrogen Generation from Lubricant under Rolling-Sliding Contact

Enami,

Yamada,

Komata

2024

Tribology Online

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Rolling element bearings in a particular application experience premature failure accompanied with white structure in steel. A possible cause of the failure is diffused hydrogen in steel which is generated by the decomposition of lubricant. This paper studied hydrogen generation from lubricant under rolling-sliding contact. A two-roller test was conducted in a sealed chamber, where the sliding speed and the lubricant temperature were controlled. The material of the roller was bearing steel and ceramic. Hydrogen gas concentration in the chamber was measured with a gas chromatograph. It was found that the hydrogen generation due to rolling-sliding contact depended on the lubricating conditions when the bearing steel specimens were used. The hydrogen generation increased by increasing the sliding speed and the oil temperature and decreasing the oil film parameter. Moreover, hydrogen generation was hardly observed under pure rolling condition. Another finding was that when ceramic specimens were used, the hydrogen generation was much smaller than when bearing steel specimens were used. These results suggest that nascent steel surface caused by the combination of metal-tometal contact and slip accelerates the lubricant decomposition to generate hydrogen.

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Effect of Surface Roughness on Tribochemical Decomposition of Synthetic Oils under High-Vacuum Conditions

Cited by 3 publications

References 14 publications

Chemical Activity of Nascent Surfaces for Tribochemical Reactions of Lubricant Components

Chemical Activity of Nascent Surfaces for Tribochemical Reactions of Lubricant Components

Hydrogen Evolution during Friction from Chemisorbed Water on Metals and Alloys

Hydrogen Generation from Lubricant under Rolling-Sliding Contact

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