Tribological aspects of nanostructured materials

The article is devoted to the review of structural factors influencing the tribological behavior of nanostructure metals and alloys without lubrication. The scientific significance of this topic is related to the understanding of wear mechanisms and the possibility of its prediction during long-term operation. Particular attention is focused on the effect of the grain size in the range of 0,01-10 µm, as one of the most important structural parameters. Emphasis is placed on materials with ultrafine grains obtained by severe plastic deformation, and nanocrystalline materials obtained by non-deformation methods of sputtering and deposition. It is shown that nanocrystalline films on the contact surface are more preferable for increasing wear resistance, since they are more resistant to structural-phase transformations during friction. Among pure metals, as objects without phase transformations, copper, nickel, aluminum and titanium are considered. As an example of more complex objects, alloys based on titanium (an intermetallic compound with shape memory TiNi and two phases Ti-Al-V alloy) are presented. In addition to the classical scheme of friction during macrodisplacement of the indenter on the contact surface, the fretting friction during microdisplacement is considered.