Quaternary Layered Boride Ti4MoSiB2: A Structure-Function Integrated High-Temperature Self-Lubricating and Negative-Wear Material

As a newly emerging class of materials, quaternary layered borides are promising structural–functional integration materials. However, there have been very few systematic and in-depth studies in many areas of these materials, including high-temperature lubrication. In this study, a novel out-of-plane chemically ordered Ti4MoSiB2 MAB phase material is synthesized and its mechanical and tribological properties are investigated over a wide temperature range. Experiments and calculations are conducted to determine its mechanical failure, friction, and wear mechanisms. The results indicate that the synthesized material maintains desirable comprehensive mechanical properties from room temperature to 1273 K and exhibits excellent lubricating and wear resistance performance at high temperatures. In this study, the operating principles of the anisotropic thermal expansion of crystals on the fracture behaviors, and the tribological chemical reactions and oxygen vacancies on tribological properties, are explained. This study is expected to provide a foundation for future practical applications in high-temperature environments.