WEAR RESISTANCE OF NANOCOMPOSITE COATINGS IN VACUUM

Abstract

One of the developing areas of tribotechnical materials science is the development and study of nanocomposite materials for movable joints operating under extreme conditions, which are not only increased thermomechanical loads and high sliding speeds, but also, mainly, the effect of a gaseous medium, in particular, vacuum. Detonation-gas spraying was carried out with the developed nanocomposite powders of the Fe-Ti-SiC-MoS₂-MgC₂ system. Particles of solid lubricant corresponding to fractions of 30-40 μm were mixed with the initial nanopowders by the wet method. To eliminate powder adhesion to the chamber walls and optimize the process of spheroidization of a mixture of its components, we used a developed and tested technology with the use of ultrasound. Tests in vacuum were carried out on a friction machine M-22PV, designed for laboratory and experimental evaluation of tribological characteristics and quality control of coatings. Investigation of the wear resistance of coatings during friction, their tendency to set were evaluated by the intensity of wear in a vacuum (at a vacuum of 1.33×10^-5 Pa). The study of the quality of surface layers, in which the processes of activation during friction proceed, were carried out using modern methods of physicochemical studies, including metallography, scanning electron microscopy, and X-ray structural phase analysis. As a result of external influences and the relative movement of the contact surfaces, the first and main manifestation of external friction arises - elastoplastic deformation, which causes the emergence of a set of surface phenomena that determine the essential properties and qualitative regularities of friction processes. The results of metallographic analysis and surface studies confirm the presence of a surface passivating film of molybdenum disulfide. The use of the optimal combination of the properties of MoS₂ and graphite films significantly improves the tribotechnical characteristics. The recommended graphite content, as established, is 10-12% (wt.%), which corresponds to the maximum lubricating effect of the formed complex film, which prevents the adhesion interaction of juvenile surfaces, while individual foci of destruction are localized in the near-surface layers and annihilate in the process of grain boundary sliding, excluding any kind of damage.