Hydrogen effect on tribological performance of lubricated interfaces

Hydrogen is being introduced as a clean energy source for heavy-duty applications to reduce carbon emissions and environmental impact. However, its application in internal combustion engines poses significant challenges, particularly regarding lubrication performance and surface degradation under pressurised hydrogen conditions. Hydrogen diffusion at contact interfaces can alter tribofilm formation, potentially increasing wear and compromising component durability and efficiency—issues that remain insufficiently explored. This study examines the tribological performance of conventional lubricants in a hydrogen-rich environment using a custom-built tribometer housed within a 3-bar pressurised hydrogen vessel. Lubricants formulated separately with zinc dialkyldithiophosphate (ZDDP), molybdenum dithiocarbamate (MoDTC), and glycerol monooleate (GMO) in base oil were tested. Surface characterisation was performed using Raman spectroscopy and scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM/EDS). The results reveal the presence of iron oxides and carbonaceous materials on sliding surfaces, which influence the formation and stability of ZDDP-, MoDTC-, and GMO-derived tribofilms. These interactions lead to variations in friction and increased wear, highlighting the need for lubricant formulations specifically designed for hydrogen-based systems.