Sensitivity of Engine-Component Wear to Lubricant-Additive and Contact Conditions Using an Antiwear Film Formation Model

Traditional engine wear models link wear rates to detailed material and contact conditions. Effects of lubricant and additive characteristics are often described by and lumped in empirical parameters such as wear coefficients. With increased environmental concern that lubricant and additives impact emissions and exhaust treatment catalysts, there is increasing interest in optimizing the lubricant and additive combination while providing adequate protection against engine wear. While the mechanisms of anti-wear film formation have been studied in great detail, engineering models of component wear incorporating lubricant chemistry are just beginning to emerge. These models build on the understanding of anti-wear film mechanisms developed and published over the years on the one hand, and on classical wear models for rough surfaces on the other. One such model has been applied to study the sensitivity of the following effects on component wear: Kinetics of ZDDP, which vary according to type and formulation, surface characteristics, contact loads and temperatures, as well as the replenishment and depletion rates of lubricant-additive to the surface-lubricant interfaces. The calculations are done for several engine components under real-world operating conditions.