Study on the tribological properties and etching resistance of Ti-DLC coatings in hydrogen plasma

The application of DLC coatings in hydrogen plasma is limited due to etching and friction-induced failure. Metal-doping is a novel strategy to improve its performance. Herein, DLC coatings with different Ti concentrations were fabricated via magnetron co-sputtering. The mechanism of hydrogen plasma etching and its influence on tribological properties were investigated by characterization and simulation. The formation of TiC nanocrystals improves etching resistance, reducing the etching rate by up to 68.8 %. A minimum friction coefficient of 0.14 was achieved, attributed to Ti-induced graphitization and hydrogen plasma-induced surface hydrogenation. MD simulations confirm the positive friction effects of hydrogen, and DFT calculations demonstrate that the strong hydrogen etching resistance of TiC nanocrystals arises from the high transition state energy barrier (∼1.54 eV). • TiC formation in Ti-DLC coatings enhances etching resistance due to a high transition state energy barrier (∼1.54 eV). • Hydrogen plasma modulates Ti-DLC friction via hydrogenation and altered carbon-hybrid bond. • Graphitization and hydrogenation minimize friction and wear in low-Ti DLC. • Preferential graphite etching by hydrogen plasma exacerbates abrasive wear in high-Ti DLC