Abstract

The mechanical and tribological properties of MXene coatings have gained notable attention in recent years due to their promising friction and wear performance. However, the chemical stability of MXenes under tribo-mechanical stress, a critical factor for ensuring long-term reliable lubrication, remains largely unexplored. In this study, we investigate the tribological behavior of a multi-layer molybdenum-based carbide MXene (ordered double transition metal Mo2TiC2Tx), highlighting its exceptional performance as a solid lubricant in dry nitrogen atmosphere when sliding against a diamond-like carbon (DLC) counterface at macroscale. Our findings reveal sustained superlubricity, with an impressively low friction coefficient of 0.005, and remarkable wear rate (5.11x10-10 mm3 N−1 m−1) over a prolonged linear sliding distance of 86 km without any sign of failure, outperforming all previously tested MXenes and 2D materials under similar conditions. Comprehensive characterization, along with molecular dynamics simulations, reveals the formation of a carbon-rich tribolayer, enabled by the enhanced tribo-catalytic activity of Mo under tribo-mechanical stress, which facilitates prolonged superlubricity. The exceptional durability and superlubricious performance of Mo2TiC2Tx coatings with negligible wear pave the way for the development of more robust and catalytically active MXenes with extended wear life and offer a promising alternative to oil-based lubricants in tribology.