Biotribological Performance of Multilayer Ti- and Mo-Based MXene Coatings

Metallic materials are extensively utilized in biomedical implants due to their excellent strength and corrosion resistance. However, friction and wear-related issues remain important challenges in load-bearing implant applications. To address these concerns, multilayer Ti₃C₂T_<i>x</i>, Mo₂TiC₂T_<i>x</i>, and Mo₂Ti₂C₃T_<i>x</i> coatings were deposited onto stainless steel substrates in two distinct thickness ranges (lower: ∼100 to 150 nm; higher: ∼225 to 275 nm) and biotribologically tested under simulated body fluid lubrication conditions. Our results revealed that low coating thicknesses of Mo₂TiC₂T_<i>x</i> demonstrated the most favorable biotribological performance, reducing the wear rate by up to 33% and consistently lowering the coefficient of friction, with reductions of up to 56% compared to uncoated references, owing to their ability to form durable tribo-films under SBF lubrication. In contrast, Ti₃C₂T_<i>x</i> coatings increased friction and wear under considered conditions, while Mo₂Ti₂C₃T_<i>x</i> showed a moderate COF reduction but higher wear rates, particularly at higher coating thicknesses and loads. These findings emphasize the superior self-lubricating properties of Mo₂TiC₂T_<i>x</i> coatings, thus highlighting their potential to enhance the durability and longevity of load-bearing biomedical implants.