Wear and Friction of Greases Containing Organic and Inorganic Sulfur Carriers

Abstract

Lithium based grease formulations are the most common lubricants used in industry today. Sulfur containing additives play a key role in improving wear and friction performance of these greases. The current study is focused on developing an understanding of characteristics of chemical bonding between sulfur carriers (MoS₂, WS₂ , MoDTC and organo tungstate ) and the interacting surfaces and evaluates their effect as anti-wear and anti-friction agents. ASTM D2266 and spectrum loading tests with varying loads while keeping other tests parameters constant were performed on the grease blends to understand effects of cyclic loading on tribochemical degradation of sulfur carriers. Tribofilms formed on the wear surface were analyzed using surface characterization techniques like SEM, EDS and Stereo Optical Microscopes. Wear scar diameter (WSD) and coefficient of friction (COF) were reported for the tests performed. This research aims to gain better insight on the atomic coordination or oxidation states of sulfur atom in additives and their correlation with anti-wear and extreme pressure performance when blended in greases.