Performance of low-friction coatings in helium environments

► Hydrogenated DLC coatings provide similar friction in helium as PTFE-based coatings. ► Application of DLC coatings prolongs running-in and provokes counter-surface wear. ► Tribology of DLC in helium depends on counter-material and contact conditions. ► Running-in in air accelerates formation of low-friction tribofilm.