Method of Performance Assessment of Lubricant Compositions Containing Nano-Additives Used for Wheel–Rail Pair

A new method is proposed for performance assessment of lubricating compositions based on industrial lubricants that contain nano-additives of different chemical composition for higher wear resistance of heavy-loaded steel friction pairs. The method is based on the joint analysis of the experimental data on the wear kinetics, change of the relative hardness, and damage in the surface layers of the metal of friction pairs. The level of structural damage to the materials in the contact zone is determined by using the statistical parameters of dispersion of the hardness values. The paper investigates the known experimental results of assessment of the level of damage to structural materials of various grades under the conditions of long-term, cyclic, static loading, and lubricated friction. It is demonstrated that the structural changes occurring in the materials during loading correlate to the changes in the statistical dispersion characteristics of hardness measurement results. Experimental substantiation of the method is carried out for steel friction pairs using lubricating compositions based on industrial oil Greaseline Lithium BIO Rail 000 by AIMOL and nano-additives of copper of M2 grade, magnesium alloy of MA2 grade, aluminum alloy of Al-Mg system, graphite of medium carbon steel grades, i.e. rail and industrial. Under system of indicators presented in the paper, the highest efficiency in terms of increase in the wear resistance of steel friction pairs is demonstrated by the lubricating composition based on industrial lubricant with the additive of nano-powder made of rail steel, as it provided the optimum value of friction coefficient, minimum damage and wear of friction surface.