The influence of nitrogen concentration on microstructure and ultra-low friction behaviour of Fe–N thin films

• Influence of nitrogen concentration on the microstructure and tribological properties of Fe–N films.
• Tailoring of nitrogen concentration and ultra-low friction coefficient of Fe–N film.
• Macrostructure and surface conductivity of the film were influenced by nitrogen concentration.

The influence of nitrogen concentration on the microstructure, chemical and electronic properties of Fe–N thin films and their tribological behaviour are studied. Increasing the nitrogen concentration from 5% to 12%, results in the decrease in friction coefficient from 0.14 to 0.04, while wear life increases significantly. However, increase in nitrogen concentration to 32% results in the increase in friction coefficient to 0.1 and decrease in wear life. Therefore, lowest friction and longest wear life is observed in the film with 12% nitrogen, which is due to the formation of ε-Fe2N phase having high bond strength and chemically passive surface.