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 Ti3C2Tx, Mo2TiC2Tx, and Mo2Ti2C3Tx 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 Mo2TiC2Tx 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, Ti3C2Tx coatings increased friction and wear under considered conditions, while Mo2Ti2C3Tx 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 Mo2TiC2Tx coatings, thus highlighting their potential to enhance the durability and longevity of load-bearing biomedical implants.