THE THEORY OF ANTIWEAR FOR ZDDP AT ELEVATED-TEMPERATURE IN BOUNDARY LUBRICATION CONDITION

Based on the experimental results from mechanical and physical analyse s, this paper proposes a theory of antiwear for ZDDP added to a base o il at elevated temperature in boundary lubrication condition. It is as sumed that the decomposition products of ZDDP can react chemically wit h one or both of the rubbed surfaces. The theory is established with p hysical and mechanical models, instead of considering the process of t he formation of chemical film. In the theory, a simplified elastic mod el is employed to predict the duration of run-in and the critical thic kness of a chemical film that should grow to achieve the antiwear perf ormance. In this model the hardness and roughness of the contacting su rfaces are the most important characteristics which control whether or not an antiwear film can be developed or the amount of wear under rub bing action. Once a chemical film is established, the growth of the fi lm is predicted with a diffusion model. The amount of the chemical fil m which is scraped off the rubbed surface can also be determined theor etically with this model. The theory also takes into account the effec t of decomposition of ZDDP on the growth of chemical film. In accordan ce with the experimental data in hand, the theory is confirmed to be c orrect.