Direct Formation of Lubricious and Wear-Protective Carbon Films from Phosphorus- and Sulfur-Free Oil-Soluble Additives

• Published in: Tribology letters Vol. 66; no. 1; pp. 1 - 13
• Main Authors: Johnson, Blake, Wu, Hongxing, Desanker, Michael, Pickens, David, Chung, Yip-Wah, Jane Wang, Q.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.03.2018; Springer Nature B.V
• Subjects: Additives; Carbon; Chemistry and Materials Science; Contact pressure; Corrosion and Coatings; Extreme pressure lubricants; Linearization; Materials Science; Nanotechnology; Original Paper; Phosphorus; Physical Chemistry; Plasma; Protective coatings; Raman spectroscopy; Sulfur; Surfaces and Interfaces; Theoretical and Applied Mechanics; Thin Films; Tribology; Ultrasonic testing; Wear; Extreme pressure additives; Antiwear additives; Additive deposition
• ISSN: 1023-8883; 1573-2711
• DOI: 10.1007/s11249-017-0945-2

Extreme pressure (EP) lubricant additives form protective tribofilms at the site of contact using the heat and pressure of contact and relative motion. Common EP additives contain undesirable elements such as phosphorus and sulfur. A novel EP lubricant additive, which contains no phosphorus and sulfur, is presented for generating lubricious carbon films. The additive consists of a surface-active molecule with a metastable cycloalkane ring, which dissociates readily during tribological contact to form lubricious carbon films. Friction and wear performance of PAO4 with this additive under a range of loads and speeds were shown to be superior to that without the additive. Optical and scanning electron microscopy and Raman spectroscopy were used to analyze the tribofilms formed on post-test contact surfaces, providing direct evidence for the formation of carbon films. Quantitative kinetics for the carbon tribofilm formation was analyzed as a function of temperature and stress, from which the activation energy for carbon tribofilm formation was obtained.