Molybdenum Disulfide (MoS2): The Lubrication Solution for Automotive Engine Pistons
Introduction
Molybdenum Disulfide (MoS2), a black crystalline sulfide of molybdenum, is one of the most widely utilized solid lubricants1. It has a wide range of applications, including but not limited to those in the aerospace/space industry1. In its appearance and feel, molybdenum disulfide is similar to graphite2.
Why MoS2?
MoS2 has a low friction coefficient, but, unlike graphite, it does not rely on adsorbed vapors or moisture2. MoS2 also has greater load-carrying capacity and its manufacturing quality is better controlled2. Thanks to its naturally low friction, liquid-molybdenum is widely used as an additive3. MoS2 particles, around 1–100 µm in diameter, maintain a high lubricity and stability at engine operating temperatures in extreme and regular conditions3.
Applications
MoS2 is often used in two-stroke engines; e.g., motorcycle engines2. It is also used in CV and universal joints2. When added to plastics, MoS2 forms a composite with improved strength as well as reduced friction2. Polymers that have been filled with MoS2 include nylon (with the trade name Nylatron), Teflon, and Vespel2.
Conclusion
The addition of molybdenum disulfide MoS2 into the lubricating grease can improve the lubrication ability of the grease, and play the role of extreme pressure additive when the lubricating film of the grease suffers from transient impact load or high heat4. There are currently no clear lubrication alternatives to molybdenum disulfide or the very similar tungsten disulfide that can resist temperatures higher than 350 °C in oxidizing environments2.
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