ASSESSMENT OF TRIBOLOGICAL PROPERTIES OF TRANSMISSION OIL WITH COMPLEXES OF MICRO- AND NANOADDITIVES

Abstract

This paper presents an in-depth experimental study of how micro- and nanoadditives influence the tribological performance of transmission oils under boundary lubrication in non-stationary friction regimes. The motivation stems from the fact that up to 30% of total energy losses in mechanical systems are caused by friction, and the optimization of lubricant formulations is one of the most effective ways to improve energy efficiency and extend the durability of friction units. Particular attention was paid to the comparative behavior of base mineral oil TAD-17i and its modified compositions.

The experimental program involved rolling with sliding and pure sliding tests, measuring friction coefficients, linear wear, and surface microhardness. The results revealed that the base oil TAD-17i alone provides only partial friction reduction (about 33%), while the addition of nanodispersed components significantly enhances lubricant efficiency. Specifically, MoS₂ and XENUM MG GEAR demonstrated the highest effectiveness: they reduced the steady-state friction coefficient by 52–56% and decreased wear by a factor of 2–3 compared to the unmodified base oil. These additives formed stable, thermally resistant boundary films capable of withstanding variable loads, start–stop conditions, and elevated temperatures.

By contrast, graphite S-1 showed limited effectiveness due to the large particle size, which contributed to abrasive wear, while XADO 1 Stage Transmission initially increased wear because of coarse active particles, although a partial improvement in surface protection was observed after a running-in period. The study further established that the dominant wear mechanisms shifted from adhesive at the early stage to oxidative, abrasive, and corrosion-mechanical types depending on the applied additive and operating conditions.

Overall, the findings highlight that the efficiency of transmission oils in dynamic operating modes is largely determined by the rheological stability of boundary layers and the ability of additives to form protective adsorption films. Nanodispersed additives, especially MoS₂ and composite formulations like XENUM MG GEAR, proved to be the most promising for extending the service life of friction pairs, ensuring smoother transmission operation, and reducing energy losses. The practical implementation of such additives in the production of automotive and aviation transmission oils opens prospects for developing advanced lubricant formulations with enhanced reliability, wear resistance, and long-term stability under non-stationary conditions.