ASSESSMENT OF SUSTAINING COUNTER PRESSURE OF IMPROVER-INHABITED OILS CONTAINING ADDITIVES OF ZINC AND MOLYBDENUM DITHIOPHOSPHATES UNDER FRICTION IN BOUNDARY LUBRICATION MODE

The article presents an assessment of the bearing capacity of oils containing additives based on zinc dithiophosphates (DF-11, DF-11k) and molybdenum dithiophosphates (PAF-4) during friction under boundary lubrication conditions. These additives are key components of modern lubricants, which provide the necessary tribological properties under severe operating conditions. The effect of the metal in the composition of dialkyl dithiophosphates on their tribological characteristics, in particular, on the bearing capacity, was studied. The studies were carried out on a standard four-ball machine using MS-20 petroleum oil as a base medium. To assess the tribological characteristics, the RD50-531-85 method was used, which allows determining the parameters of the linear approximation of the dependence of wear intensity on contact pressure: wear coefficient (k) and bearing capacity p0. This approach provides a more in-depth analysis of the tribological properties of lubricants, taking into account contact pressures during wear. The obtained results showed that zinc-containing additives provide a significantly higher load-bearing capacity of the lubricating layer (1235 MPa for DF-11) compared to the molybdenum-containing additive (1038 MPa for PAF-4). This indicates that they form a stronger and more wear-resistant boundary film. At the same time, the molybdenum-based additive demonstrated better antifriction properties, showing the lowest friction coefficient. Thus, the study shows the difference in the functional action of the additives: zinc dithiophosphates act as highly effective antiwear components that increase the ultimate load, while molybdenum dithiophosphate manifests itself primarily as a friction modifier. The obtained results are important for the targeted development of oil formulations for specific operating conditions.