Researchers from the Faculty of Mechanical Engineering (UL) have demonstrated that high-performance Diamond-Like Carbon (DLC) coatings can significantly improve the service life of polymer gears operating under demanding conditions. The findings represent an important step toward the development of more efficient and sustainable power transmission systems.
Polymer gears are frequently used in powertrain applications due to their low weight and low noise operation; however, their limited wear and fatigue resistance remains a challenge. While numerous studies have shown that surface coatings can greatly enhance the tribological properties of metal components, much less is known about the impact of DLC coatings on polymer gears.
In the article “High cycle fatigue and wear behavior of ta-C and a-C:H coated PEEK polymer spur gears under dry contact conditions”, published in the prestigious journal Polymer Testing (IF = 6.0), our researchers were the first to experimentally investigate the performance of PEEK polymer gears coated with ta-C and a-C:H of various thicknesses. The gears were tested in a reference gear pair against a steel gear in accordance with VDI 2736 guidelines. All tests were conducted without lubrication, at a torque of 1.8 Nm.
The results show that thin coatings (2 μm) wear off quickly and do not provide a significant improvement in the service life of polymer gears. In contrast, thicker coatings (5 μm), despite wearing off relatively early, substantially enhance the gears’ resistance to fatigue. Gears coated with ta-C (5 μm) and a-C:H (5 μm) achieved approximately twice the service life compared to uncoated gears. The a-C:H coatings emerged as the best performer, as they caused noticeably less wear on the steel counterpart gears compared to the ta-C coatings.
“Our research proves that the correct choice of DLC coating thickness and type can significantly enhance the performance of polymer gears in real operating conditions,” emphasizes the first author of the study, Assist. Dr. Bor Mojškerc. The leading author, Assoc. Prof. Dr. Nikola Vukašinović, adds that the findings are highly valuable for the future development of advanced lightweight power transmission systems.
Link to the article in Polymer Testing: https://doi.org/10.1016/j.polymertesting.2025.109009