| Abstract: | The temperature of surface asperities affects lubricant‐surface tribochemical interactions. It is important to know the nature of this to identify ways of preventing scuffing and seizure under extreme‐pressure (EP) conditions. A new model for the determination of the temperature of contacting asperities is presented in this paper. It assumes the superposition of thermal processes occurring on the macroscale and thermal phenomena in the contact of asperity tips (microscale). Numerical results have been obtained for conditions of four‐ball testing of various lubricating oils — a mineral base oil with and without antiwear and EP additives. To calculate the scuffing and seizure temperatures, knowledge of the mechanical and physical properties of the test ball material (bearing steel) and lubricants, as well as the parameters describing the surface topography of the balls, was necessary. Friction coefficient curves were also needed; they were determined during four‐ball tests with a continuously increasing load. For the base oil with lubricating additives, the temperature of contacting surface asperities at the moment of scuffing initiation was calculated to be about 230°C and increased to over 1000°C at the highest loading of the four‐ball tribosystem. This suggests the possibility of tribochemical reactions of the lubricating additives with the steel surface, and diffusion of some elements, a modified surface layer having good antiseizure properties being produced. Such a layer prevents seizure of the tribosystem. For the base oil without lubricating additives, scuffing initiated at about 150°C and the temperature exceeded 1200°C at seizure. The temperature values obtained agree with results in the literature. |
