The scientists from the Institute of Problems in Mechanical Engineering of the Russian Academy of Sciences conducted a unique study aimed at studying the influence of microbial populations on the tribotechnical properties of plastic lubricants. They found out that the use of serpentinite mineral and Aspergillus niger fungus in lubricants opens up prospects for increasing the durability of rubbing machine parts and mechanisms, as well as reducing energy consumption to overcome friction forces. The results of the study have been published in the scientific journal High-Tech Technologies in Mechanical Engineering.

It is known that the number of microorganisms in the environment varies from units to thousands. The air environment around the operating mechanisms is saturated with bacteria and fungi that can get inside lubricants both before operation and directly during the operation of the equipment. Even the most modern and high-quality lubricants are subject to biological effects, which reduce their performance and contribute to damage to the surfaces of the rubbing elements. However, despite significant progress in the study of friction and wear processes under conditions of mechanical loads, temperature effects and chemical composition of lubricants, the impact of microorganisms remains an insufficiently studied factor. Most of the studies consider only traditional risk factors such as mechanical impurities, dust and abrasive particles. Biological objects are practically ignored, although they are the ones that can have a significant impact on the surface condition of friction pairs. For the first time, the IPMash RAS scientists have performed a large-scale scientific study, revealing important mechanisms for the formation of antifriction and anti-wear properties of a number of domestic lubricants.

“It was found that the addition of a combination of serpenitite and Aspergillus niger increases anti-friction indices by 17-40%, depending on the type of lubricant. Pronounced synergy is observed for most samples: an increase in protective qualities reaches about 18%.

Anti–wear characteristics increase by 11.5—34.6%, however, some samples show a slight deterioration in these indicators,” said Alexander Breki, a leading researcher at the Friction and Wear Laboratory at the Institute of Problems in Mechanical Engineering of the Russian Academy of Sciences. It should be noted that Aspergillus niger mold is often found in industrial environments.

Serpentinite has long been used in some machine components due to its positive effects on reducing friction coefficients and improving the wear resistance of mechanisms. However, the combined presence of two such different substances has not been studied in detail before.

The obtained indicators confirm the importance of taking into account the presence of microorganisms in the composition of modern lubricants, since the correct combination of useful compounds provides significant advantages in the operation of equipment. Within the framework of the project, the scientists have developed two key mathematical models capable of describing changes in the most important indicators of the functioning of friction units — the force of friction and the rate of wear.

When developing the model, the scientists had to take into account two factors at once — the presence of dispersed additives of mineral origin and living organisms. The final dependence shows how strongly the concentration of microorganisms affects the magnitude of the friction force. The greater the proportion of microorganisms, the more the friction force changes, which is associated with physico-chemical changes in the structure of the surface layer of the lubricant.

In addition, a model was developed reflecting the relationship between the amount of mineral additives and the level of presence of microorganisms and the intensity of wear on the working surfaces of parts.

This knowledge makes it possible to optimize the composition of lubricants in such a way as to minimize damage to parts and increase the service life of machinery. The conducted experimental studies confirmed the theoretical calculations. In particular, the dependences between the indicators of friction and wear, the level of serpentinite content and the number of microorganisms in the lubricant composition were obtained. The results obtained indicate the possibility of targeted control of the lubrication process by selecting the optimal ratio of minerals and microbiological load.