Thermodynamics of boundary lubrication and scuffing

Abstract
The critical temperature of scuffing found in some lubrication systems is identified with desorption of the surface active agent in the lubricating oil. The thermodynamics of the system are considered and then applied to the chain matching of carrier and additives. Chemisorption takes place more readily on a martensitic steel, which is reactive, than on austenite, and thus masks the physical desorption and so hinders scuffing. This is the reason that in industrial gears retained surface austenite is avoided. The surfactant adsorbed on the metal can inhibit corrosion and prevent extreme pressure additives from forming a protective layer on the surface. This explains the widely known phenomenon of additive interference and increases the understanding of scuffing and running-in.