ULTRASOUND TREATMENT OF MODIFIED LITOL 24 LUBRICANTS

A comparative assessment of tribological properties of Litol 24 lubricant with the addition of 1 % hexagonal boron nitride (h BN) and 1 % tungsten disulfide (WS2), followed by ultrasonic treatment, is carried out. Microstructural analysis shows that ultrasonic cavitation promotes the breakdown of agglomerates and the homogeneous distribution of fillers in the lubricating medium. During tribological tests, it was recorded that introduction of 1% WS2 and 1% h BN, followed by ultrasonic treatment, reduces the friction force by 29–30% and 17–20%, respectively, compared to the base lubricant under a load of 40 N. At the same time, h BN shows more effective heat removal from the friction zone, which is due to its higher thermal conductivity. It is found out that WS2 is the preferred modifier for friction units operating under high loads and moderate temperatures, whereas h-BN is recommended for high temperature operating conditions. The obtained results confirm the effectiveness of ultrasonic dispersion as a method that allows the beneficial properties of nanoscale additives in plastic lubricants to be fully realized. The study objective is to evaluate the effect of ultrasonic treatment on the particle distribution pattern in the base lubricant and on the tribological properties of the resulting modified lubricants. The task the paper is devoted is to justify the choice of a modifier (WS2 or h BN) for specific operating conditions of friction units, based on the analysis of their effect on the friction force and heat generation in the friction contact zone, as well as to determine the effectiveness of ultrasonic treatment as a method for homogenizing nano additives in a highly viscous lubricating medium. The novelty of the work lies in conducting a comprehensive comparative assessment of the tribological properties of Litol 24 lubricant, modified with WS2 and h BN nanoparticles at equal concentrations (1 %) using ultrasonic dispersion, as well as in finding the correlation between the impact of each modifier under boundary friction conditions at a load of 40 N within the rotation frequency range of 200–800 rpm.