Quasicrystals, materials with a unique atomic structure that combines order and aperiodicity, are of considerable interest due to their potential applications under extreme loads. Studying the tribological properties of quasicrystals, especially in vacuum where atmospheric influences are excluded, is critical to understanding the mechanisms of friction and wear at the atomic level.
Research shows that quasicrystals have a low coefficient of friction and high wear resistance compared to traditional materials such as metals and alloys. This is due to their complex crystalline structure, which hinders dislocation sliding and plastic deformation. In a vacuum, the absence of adsorbed layers of gases and moisture enhances these effects, leading to even lower values of the coefficient of friction.
The wear mechanisms of quasicrystals in a vacuum also differ from those in atmospheric conditions. The processes of adhesive wear and abrasive wear at the atomic level predominate. The formation of thin films of oxides or other chemical compounds on the friction surface is practically excluded, which helps to maintain low surface energy and reduce adhesive interaction.
Despite the progress made, the understanding of the tribological behavior of quasicrystals in vacuum remains incomplete. Further research is needed to identify the key factors influencing friction and wear, and to develop new quasicrystalline materials with improved tribological properties for use in aerospace engineering, microelectronics, and other fields.
To reliably study the friction and wear processes of quasicrystals at room temperature, we tested pressed samples in a vacuum environment with a residual pressure of less than 10−5 mbar. Spherical samples of hardened steel were used in friction and wear tests. The results of the experiments in vacuum demonstrate significant differences in the change in the friction coefficient depending on the total sliding distance traveled for Cr steel sliding on aluminum oxide, a true quasicrystal, or high-carbon steel. Clearly defined minima of the friction coefficient of the oxide film and adhesive forces are observed at the contact of the quasicrystalline and metal surfaces. Typical friction values obtained in high vacuum are at least twice lower than at normal atmospheric pressure, indicating a significant influence of the environment on tribological processes. In this paper, an interpretation of the observed differences between the samples is proposed based on their chemical composition and potential interaction with steel. For the first time, based on the measurements carried out, an estimate of the real surface energy of a quasicrystal was obtained.
Author: S. Kenzari, D. Bonina, J. M. Dubois, V. Fournée
Institute: LSG2M (UMR 7584 CNRS-INPL-UHP), Nancy School of Mines, Laboratory of Materials Science and Metallurgy, Center for Materials Science, Parc Sorup, Nancy, F-54042, France, Austrian Research Centres, A-2444 Seibersdorf, Austria