MEPhI scientists as part of a scientific group have developed a unique solid lubricant for high-precision equipment, which is suitable for working in extreme conditions. According to them, the composition based on tungsten, sulfur and selenium reduces friction several times better than analogues. The results of the study were published in Nanomaterials (https://www.mdpi.com/2079-4991/13/6/1122).

In mechanical engineering, liquid lubricants are commonly used. However, they cannot be used in extreme conditions - for example, in spacecraft nodes or inside vacuum manipulators and microelectromechanical devices. This requires solid lubricants.

MEPhI researchers in collaboration with colleagues from the Immanuel Kant Baltic Federal University developed a unique solid lubricant with an original nanostructure. It is based on tungsten sulfoselenide with evenly distributed spherical nanoparticles of pure tungsten.

The new lubricant significantly outperforms analogues based on disulfides or diselenides of molybdenum or tungsten in terms of efficiency and wear resistance, noted Vyacheslav Fominsky, one of the authors of the development, chief researcher of the Department of Solid State Physics and Nanosystems of the MEPhI.

“We managed to find the optimal combination of the “matrix” material and nanoparticles, which allows us to achieve increased hardness and plasticity of the lubricating coating. During friction, a nanofilm (tribofilm) 20 nm thick is formed on the surface of the coating, which significantly reduces friction due to the weak interaction between atomic planes in its structure,” he said.

The experiments showed that the coefficient of friction for the resulting coatings at room temperature did not exceed 0.02, compared with 0.04 - 0.07 for analogues.

“By changing the sulfur content in the amorphous matrix, we can create high-quality lubricating coatings for difficult operating conditions, such as when friction units are strongly cooled (down to -100°C) in an inert atmosphere at a low concentration of water vapor,” added Vyacheslav Fominsky.

To obtain such coatings of the required structure, scientists used a modernized method of reactive pulsed deposition.

“We used laser evaporation of tungsten diselenide in hydrogen sulfide, which resulted in the formation of an atomic stream of selenium, sulfur and tungsten and tungsten nanoparticles. The coating was deposited at room temperature of the substrate. The laser deposition method makes it possible to flexibly adjust the composition and structural state of coatings and opens up the possibility of obtaining materials with super-lubricant properties under various conditions,” the scientist noted.