Lubricant Degradation and Related Wear of a Steel Pin in Lubricated Sliding Against a Steel Disc

Abstract

In lubricated sliding contacts, components wear out and the lubricating oil ages with time. The present work explores the interactive influence between lubricant aging and component wear. The flat face of a steel pin is slid against a rotating steel disk under near isothermal conditions while the contact is immersed in a reservoir of lubricant (hexadecane). The chemical changes in the oil with time are measured by vibrational spectroscopy and gas chromatography. The corresponding chemistry of the pin surface is recorded using X-ray photoelectron spectroscopy while the morphology of the worn pins; surface and subsurface, are observed using a combination of focused ion beam milling and scanning electron microscopy. When compared to thermal auto-oxidation of the lubricant alone, steel on steel friction and wear are found to accentuate the decomposition of oil and to reduce the beneficial impact of antioxidants. The catalytic action of nascent iron, an outcome of pin wear and disk wear, is shown to contribute to this detrimental effect. Over long periods of sliding, the decomposition products of lubricant aging on their own, as well as in conjunction with their products of reaction with iron, generate a thick tribofilm that is highly protective in terms of friction and wear.

Ultralow Friction and Wear of Polymer Composites under Extreme Unlubricated Sliding Conditions

“…Distinct C groups have been detected from the tribofilm. As seen from the C 1s spectra, the peaks at 284.5, 284.9, 285.1, and 285.5 eV corresponding to CC, CC, CH, CN bands are identified, whereas the peaks at 286.2 and 288.4 eV correspond to CO and CO bands . The presence of CO and CO bands indicates that thermal pyrolysis of PI and reaction of PI with O 2 or water vapor in atmosphere occur.…”

Tribological properties of polyol-ester-based lubricants and their influence on oxidation stability

“…Nascent metal surfaces are believed to be much more chemically active than oxidized surfaces and are both reactive with lubricants and act as catalyst in various chemical reactions. 17 (3) Wear debris . 24 Although less active than nascent metal surface, wear debris are also considered an effective catalyst in the chemical breakdown of lubricants.…”

Comparison of the oxidation resistance of synthetic ester oils DOA and TDTM: Experimental evaluation and theoretical calculation

“…The transformation of molecular structures is detrimental to the performance of lubricating oils . Many studies have investigated the oxidation of hydrocarbon oils, and the free‐radical chain oxidation mechanism has been proposed . However, the oxidation process of ester linkages is different to that of hydrocarbons due to their unique characteristics, and the oxidation mechanism of hydrocarbon oils does not satisfactorily explain the oxidation of synthetic ester oils.…”

“…6,7 Many studies have investigated the oxidation of hydrocarbon oils, and the free-radical chain oxidation mechanism has been proposed. [8][9][10][11][12] However, the oxidation process of ester linkages is different to that of hydrocarbons due to their unique characteristics, [13][14][15] and the oxidation mechanism of hydrocarbon oils does not satisfactorily explain the oxidation of synthetic ester oils. Several studies have reported structures of degradative products of diesters, whereas the structural details of polymerized products resulting from oxidation, as well as the polymerization mechanism, remain unclear.…”